Aln Tel, I'm a frequent user of this forum, not a moderator, but about the only time a post is deleted is if its either obscene or considered to be spam.
Its likely that you've replied to a post that was duplicated in more than one forum. That is discouraged, but happens on a daily basis.
Keep posting.
Dear reader,
I have recently discovered the fabulous community of the CNET forums. I myself am a fairly advanced computer user/technician, and I enjoy browsing the forums and try to help those which I can.
Recently, I have been very troubled. I notice posts that I have already answered, yet when I go in, my post is missing. I completely remember already answering this post, yet... It's not there. Is there something wrong with my head? Or is someone deleting my posts? I have not posted anything obscene or inappropriate at all.
Is it because someone is deleting my posts for some reason? Or could it be because somebody posted their problem on more than one forum? Or am I just plain stupid, with my frequent feeling of deja-vu?
Could a moderator, or someone with previous experience let me know what the heck is wrong?
Please reply here, or send me a mail by clicking on my name right after this message.
-AInTeL

Chowhound
Comic Vine
GameFAQs
GameSpot
Giant Bomb
TechRepublic