I not only made comics friends, I ended up engaged to somebody I originally came across on a comics making forum, so yeah, this stuff can definitely happen!
It's usually easiest to look for comics creators who make work with a similar vibe or in a similar sort of community to you. I'm personally in a few communities, like one with UK print people I've known for years since my small press days, and then others with Tapas people, like one where LGBTQ+ Tapas people hang out. People you have something in common with, like rough level of achievement, experience or ability, drawing style, genre or themes or being from a similar region or community tends to make it easier to be friends because there's common ground to build on. With my UK friends, we've all worked professionally to some extent, so we can talk about the industry, high level craft discussion, how Brexit is messing up everyone's attempts to send out their kickstarter rewards (UGHHHH), and with LBGTQ+ friends it's often talking about social justice issues in webcomic communities or being excited about relatable queer content in each others' comics.
The best way to start is to look for somebody you totally feel like you're on the same page with, like say they wrote a post on the forums you just 100% empathise with, and just send them a message like "yo, you seem really cool! I loved your post!" or just... follow somebody's comic and say "wow I really love this comic, it's totally my jam!" and start commenting regularly. Basically, engage with people's work and give out sincere compliments if it resonates with you.