Recently I saw a question that (I believe) was valid, but it had -2 rep. Has OP committed some Stack Exchange faux pas? Why was OP downvoted? (here: Comma before 'only to')
Aside from the single quotes used to quote "only to", I see no problem with this question. The Help Center wasn't particularly helpful; it doesn't make any reference to downvoting questions (only saying that, through voting, "good answers will rise to the top" and implying that bad answers are meant to be downvoted).
I apologize for my ignorance of what may seem like common knowledge; I'm pretty new here.