Some issues with imageboards

I've been noticing a few issues lately with replies on imageboards and felt like I needed to ask about it.

I've encountered reply-blocks on 4chan, not4chan, Ko-chan and 7chan. I managed to simply add cookie blocks on the three first to solve the problem, but 7chan still returns a 403 page if I reply.

I just wonder if there is something extra I need to change or if the 7chan 403 is unrelated to the reply-blocks that seemed to be to counter spambots on imageboards. And of course, if it is unrelated to the anti-spam code, it would be nice to know how to solve it.

If you block the referrer header you get a 403. I normally have this disabled in Firefox and recently I started getting these errors when trying to post. If you're using Firefox, go to "about:config" (without the quotes) in your address bar.

network.http.sendrefererheader should be set to 1 or 2
Google this parameter for more info on what each setting does