I don't tend to feel ignored on forums except for the busier ones, where the rule of familiarity is taken to the extreme and people who post fifty times a day but talk over everyone else or contribute nothing receive more attention than people who post less but contribute and show concern for others. I leave those pretty quickly, because it's a toxic atmosphere unless you're either very self-centered or need to kill time.
The Internet is one big grab for attention, though, so I don't know what else to expect. Finding little oases is nice.
I tend not to comment on other posts because experience has shown me that people tend not to talk back very much on support forums. I'll try sometimes, but it feels contrived to throw out "Good job!" and "Me too!" all the time, and it's unlikely that longer, more open-ended posts will be responded to. Quite a few people don't talk back on their own threads, so I usually cut short the effort I put in.
Maybe when my anxiety and depression was severe any interaction at all would have been bolstering, but at this point where I just sweat half to death during interviews and mentally fumble when people talk to me offline it doesn't make much of a difference. I like wasting time and I keep up the hope of meeting the occasional kindred spirit or brainstorm buddy, but it's limited. I could be spending the time and effort I spend on a longer, more honest post like this talking to my family or people I already know who won't just think "tl;dr".
It's all pretty bad for my self-esteem, and my levels of depression are directly related to how much or how little time I spend on forums (all forums). No amount of "Good job!" or "Me too!" responses is anything close to meeting someone who thinks my ideas are interesting enough to pick apart over a drink. My self-esteem and feelings of belonging rose the most when I started meeting people who cared about and took me seriously enough to do this. Before that I was just Poster #231456 and Good Deed #53223.