I definitely have an inner monologue and talk to myself often. Mostly to work through problems and also imagining how scenes play out. Honestly, I sometimes have a better time by myself, day dreaming or talking to myself than taking to strangers.
My inner monologue won't shut up sometimes. 
Like as I'm typing this, I'm hearing my inner monologue saying it and also telling me what to say next. My imagination is also pretty vivid and sometimes I just go into daydream mode and just sit there thinking of everything under the sun.
Funny thing is I asked my brother one time and I guess he doesn't have an inner monologue. I can't even imagine what it would be like to not hear yourself talk all day (in your head).
Oh, boy! I can't resist these psychological topics!
If what I write is too long, I'll leave a TL;DR at the end.
Here we go:
Having inner monologues might not sound that healthy or reasonable, but if you hear me out, you'll understand why this may be a productive practice:
first: putting thoughts in words is extremely valuable since sometimes we don't get what we're feeling. Yeah, we may feel a mix of emotions, however, we don't get exactly why. We're so concerned about the emotion explosion in itself than asking why we're having a hard time dealing with it. Deconstructing the thoughts in words makes you realize your feelings' motivation, which usually gets clouded by your nerves.
second: having a second voice to debate with is a blessing even if you're alone. This allows you to face contradictory arguments within your line of thought. Once again, as soon as you start monologuing you ask you some questions about a specific concern, and once that question is made, you direct your brain on thinking about answers to that dilemma you may be facing. Even silence might enough to you back in your tracks.
and third (I'll end with this one): this makes you constantly exercise your brain. Everything you think about is making you evolve your rational thinking. Of course, you can imagine silly things here and there, but when you encounter something you can't get over with, this is the point where you start thinking about resolutions. This way, you'll ponder about hypotheses and outcomes, which tends to orchestrate your view about what you should do over what you should not.
TL;DR: Monologues are healthy if done right. You may direct your brain in better ways than you think by putting things in words as you may find solutions that were once clouded in your head.
Still, dialogues are very valuable as well.
To digest something complex you must first deconstruct the idea in simples topics.
That's where our reason is born anyway: within the principle of the doubt.
Who are we to judge badly something so important and productive such as the monologue?
I voted "I'm not sure" because... honestly, I'm unsure?
I do have discernible thoughts but I don't exactly hear them with a voice, like many people seem to describe. Or rather, I don't hear them in my own voice or any other specific voice, it's just... words and sentences appearing in my brain, as neither text nor speech. Does anyone else feel this way or am I just weird?
My train of thought is chaotic and uncontrollable (though that's probably because of ADHD), and rather like talking to myself in my head, it's like having 20 different people talk at the same time and trying to make any sense out of that (falling asleep with that constantly going on is fun 
)... But again, I don't "hear" them. I talk to myself out loud all the time but it's not exactly an "inner" monologue once you verbalize it, lmao.
The only text running through my brain either comes from memories or imaginings of other people (real or fictional) or if I'm reading words written by someone else. From my own voice, it comes when I'm thinking and plotting of something to say or write or if I just think of commentary that I would never type out/say publicly like "Wow, this is bad." It's like playing videos or sound bytes in my head.
Other than that, most of my thoughts come as imagery to me. I don't have a narrator that just goes on and on inside.
I feel like my insecurity and anxiety talks to me whenever I experience something embarrassing or overthink situations, basically scolding myself for the actions I've taken and regretting them. It sucks but it is what it is 
I tend to overthink a lot, thus my inner monologue.
2 months later
It's one of my worst skills, maybe because i'm a pantser when it comes to writing dialogues and monologues. Always envy those who can come out beautiful lengthy monologues like in Beastars.
No, no, not like that. What I was asking was whether or not you have an internal voice. Here's the definition.
My inner monologue shifts between plotting my series, daydreaming that I'm a fierce, warrior queen, and the negative- no one is ever going to love me and I'll never be more than the "lady's maid"/built-in babysitter. (I am trying to improve my self talk but it's hard.)
oh sorry 'bout that. I thought it's about the characters.
I personally don't self-talk like characters, at least not in full sentences.
All the time.
That's how I write screenplays. I simply put myself into the script and "act" the way I want it to look on screen. I imagine every script writer does that though. 
As far as comics, it's the same thing. But you have to keep tabs on your characters, how they act, what they are like, their motivation for each scene, etc. When you know your characters inside and act, you can "act" for them, and make the dialogue POP.
I was bitten by the Hollywood bug early in life and took some acting classes. So, when I have two or more characters that share the screen, I just "act" for all of them. I worked on a TV series project once that featured five men sharing a brother's mansion together, who had just lost his wife, and it was a sitcom. So I had to act out five different people, with completely different characteristics. I had to sit at my desk and envision the scene, and then "play" it out.
It's quite a talent to have and honestly, if you don't mind looking silly about it, I heartily suggest every writer give it a shot. You'll do much better when it comes to dialogue, for sure. 
I'm not really talking "through characters", I mean more like in every day life. Do you have conversations with yourself?
wow... the 'no' % is that low....! no wonder no one understand me...
I'm feeling all weird now... but my thoughts are almost exclusively visual, or sensual... colors, textures, music... but definitely no inner voice talking... sometimes, i do picture words, and link between words, like a organized structure of words...
Conscious or unconscious (like in dreams), I'm visualizing my thoughts. I always put that on the account of juggling with too many languages (chinese french english), so even when I argue or discuss with people, I'm using a lot of drawing, graphs, figures, gesture, to express my ideas... I'm awful at speeches...
You made me realize that my comics is the same somehow. I'm trying to visually conceptualize a notion or concept... so I translate a word in image, because that's that my brain does...
I wouldn't say I have full-on conversations with myself, it's more like:
"Man the intricacies of the effects on social media is so interesting. I wonder if people have made studies about it. Which reminds me, I should probably do my research assignment. Man, I really don't want to do group assignments right now... I want to work on my comic. Oh yeah, plot point a should be in season 1, instead of 2. I wonder how I can put more scenes of character development in that part of the story-"
Does-does that count?? lmao-
I can play through a memory or a hypothetical scenario, like a scene in my head with a lot of clarity, with voice performance, visuals etc. but I don't have a single ongoing narrative in words in my head as a natural. My thoughts aren't linear enough, so it's really just more like a constant riot of sensations and ideas flying off in all directions. Occasionally for fun I might narrate my life as I do it in the style of a book I've been reading, but it's not how I operate by default.
Chances are, if there's a conversation or monologue running through my head while I'm doing something, it's completely unrelated to the thing I'm doing. If I tried to make a character in a comic whose "internal monologue" was like mine, it'd be like... their head would be surrounded by five different fragmented ideas tangentially related to what's going on in any given panel, which might be words or images.
Playing through a scene with imaginary characters is more like a coping mechanism I developed as a kid to escape from the overwhelming chaos of my brain's natural tendency to over-process and over-think every little idea and bit of stimulus. Scenes are linear, so it's relaxing to just block out everything else and focus on this one scenario.
According to my experience, you CAN'T create a story, any story, without talking it through, whether it's out loud or in your head. At some point, you open your mouth or your mind, and you visualize what someone will say or do.
See, some people can just think these thoughts and not actually "talk". Me, I most certainly have to talk. I can't visualize until I actually HEAR what my characters are saying, and how. if they have accents especially, I need to HEAR it. Even if I'm writing a scene with no dialogue at all, I have to hear what is going on to help me work it out.
Also, I have a terrible stammer since I was two years old. It's hard for me to speak to others so me talking to myself while I work out a script or comic panel, or book, or story, is my way to practice. I don't stutter if I talk when no one's around to hear.