When I first started my comic I got a decent chunk up and then made a post saying "I've got a scifan comic about giant robots, who's got some similarly niche scifan for me to check out" and that got me some subs who are still wit me and helped me find some comics I'm still following. It worked. I've even been trending a few times. I also got a few recommendations.
I'd say I'm more of a fan of recommendation threads, and I am in theory, but the problem then comes like with the front page that people will just recommend the same few more popular creators over and over unless you're very specific about what you want.
But honestly, with things like post your latest update threads and plenty of other appropriate places to link your comic during your average conversation, there's no need for these dozens of bog standard share you comic self promo with no limits threads. I think the more specific these threads can be the more likely you can get the readers who are genuinely interested and the more likely you won't just get swept up in a wave of newcomers spamming their comic in every self promo thread around, not that specifics always stop them just not reading and spamming it anyway. I think some of the nicest balance can be you can promo yourself as long as you also promo someone in the same genre or a smaller creator as well, but forcing restrictions on people can definitely be unpopular.