This forum doesn't require you to be a furry. I'd say the only condition is that you be a fan of the comic. No one will start ignoring you if you make a human or anthro avatar of yourself and post art in the forum. If your human drawings are getting less responses than you expected then it's not because as a forum we look down on them as non-furry. Sometimes certain topics/pictures just don't get the volume of audience you were hoping.
I think it's also safe to say that all of us in the forum are mature enough to not mind if a newcomer/older member does or doesn't have a fursona. We don't judge you or accept you based on having one or not. Personally I don't even equate forum members with their fursona's (if they have one) and sometimes have to remind myself what they are.
You brought up the phrase "Four legs good, two legs bad". A few members use birds as fursona's. And I think Tom Flapwell is a bat (I'm not sure, like I said I don't always know who's what).
I'd like to take this point to make clear that despite my nick having 'raven' in it and going by the name of Muninn (a mythological raven) in the chat I don't have a fursona and am not a furry. I just happen to like birds (the human variety too

).
As others have said, just do what makes you feel best.