If it's me i'll find it annoying. Because if i go to comment section, i'm there because i want to talk or read people talk about that comic, especially on webtoons, you almost can't miss the comments because almost everytime it's super funny/interesting XD So if i enconter "hey check out my comic paste link", it'll be annoying since it's not why i go there, and if you do that enough times on a lot of comics or even all, i'd start to take note to not read your stuff even if i find you via other media ;v;
I think the creator theirself probably don't care since it don't effect them anyway, the one who'll be bothered probably are the readers, especially if they're the hardcore ones, you'll get quite the cruel treatment ;w;
So i'd suggest you to not do it, even if promoting is a struggle doing this actually will make everything much more of a struggle, especially if some hardcore fans decide they don't have better things to do and treat you badly.
Uploading to webtoons is a good enough thing, since there's a real lot of readers there. Even if you only keep posting as usual you'll gain new readers.
Another way to boost it a little bit is probably encourage your readers to share, make a lot of social medias account, like a lot, instagram, discord, tapas, twitter, facebook, reddit, do everything if you can. Because the more accounts you have the better the probability is. But like, don't leave your account hanging, post stuffs and whatnot 
Also try to collaborate with others, especially on ig, there's a lot of collaboratioes.
Maybe it'll help if you make small event (not specifically on ig) to share your work and if x amount of new reads/subs reached you'll draw some fan service or something, depend on what your readers want best.
Or contest on who can share the most (tell them to ss people they share it to, and the one who have the most ss win (on stuffs like this there's usually a rule where you need to post in group chats of 10+ members, so it's proven they're not lying)) win a quick sketch of their request.
There's a lot you can do if you decide to hold a contest/event.
Always replying to people on your comments help too, people who don't sub might sub because you're kind and have enough free time to reply to them, especially if you do this consecutively.
And as ottogruenwald said, if you really want toshare via other comics, choosing one that have the same genres with you will work better, since their readers like the genre your comic also have. And you have todo that by contacting that other comic creator, since creator's word will have more impact than if you comment out of nowhere.
Anyway, i think doing that will do more harm than good to you.