Poll results are only an 'argument from popularity' if you use the results to make a claim other than, "these people think x".
If a poll finds that 60% of Americans believe in creationism, then saying that 60% of Americans believe in creationism, is not a logical fallacy. Saying that 60% of Americans believe in creationism therefore it's correct, is an 'argument from popularity'.
A poll revealing that the denizens of the SGU forum do not think an advertising signature is lame or inappropriate, reveals just that, that the SGU forum doesn't feel it's lame or inappropriate. The nature of the question is different to creationism though, because this is value judgement and not a scientific question. Thus there is no legitimate authority on whether it's actually "lame", and the authority on whether it's appropriate lies with the mod team (who say it's fine).