Why do some posts require mod approval and others don't?

[akpak]

I'm trying to post some tips to one of the game forums, but it has never appeared in the thread. The first time I thought the forum just ate it, but the second hasn't shown up either.

If I do a short reply in the thread, it goes in immediately. A longer post, and it says it needs mod approval. If I try to post the first tip just on its own, it says it needs mod approval.

Seriously, why is this happening? I'm not trying to spam anything... I'm just trying to answer some questions >.<