It seems for me that it happens on longer threads.

Strange that there is no post #5 in this thread.

I'm just receiving random " someone quoted your post " aka forum replies .

yeah, it doesnt let me post either. wtf?

Only short posts work for me. Long posts are deleted.

I'm having the same issue with some threads, took me 10 minutes to figure out how to post two sentences.

It is rather annoying. I found out that I could not post replies for some strange reason.

I found that if I typed one sentence, posted it, then went into new post and typed a 2nd sentence, it would append it to the first post, but the formatting would be off.

I have the same problem. Two posts and one topic not visible

90% of my posts get deleted for no reason whatsoever, soon as they're posted they never appear.

No, I can't ;)

I've had issues with posts disappearing but usually it's when I go to browse other parts of the GOG site while the post dialogue is open. I've even had issues with it when I use a different tab.

Or sometimes if I'm not on the last page of a thread (eg. posting from the first page), it'll eat the post.

But generally, if I'm at the end of the thread and I don't go off anywhere else on the site, in that tab or another, I don't have problems with it.

If you have low rep you can't post urls. It's temporary:
http://www.gog.com/forum/general/is_the_gog_site_and_forum_always_50_broken_or_is_it_just_a_christmas_thing/post28

It happened to me twice last week, and I had to re-write them again... one was a really long post in Classifieds (the very first I made that took like 40 minutes to prepare and write...)

I noticed the second time that for some reason, it took a long time to reload the page after posting, only to find out there was nothing posted by me.

I don't know why but this is frequently happening with me, 75% of my posts won't show up.