I have to agree with the "depends on your comic and audience" line of reasoning.
If your comic isn't very good, putting up comments or forums is asking for people to insult your hard work.
The same is true for social media. I've started posting links to my comics on reddit. I know my stuff sucks, but unless I keep doing it, it will ALWAYS suck. I'm trying to determine if the negativity is worth the number of new people it funnels my way. I've never had more than tens of people in one day, but after posting to reddit I had nearly 200. For me, that is huge. What I'm hoping is that if 95% hate my stuff, 5% might NOT hate it and come back.
For now I don't have comments or a forum. If I get good enough to attract a bigger audience, I'll reconsider.