Why my posts are triggering spam filter?

I don't think so, we are using pretty standard Drupal modules + a custom blacklist, so I doubt that Cyrillic characters could trigger that. Pay attention not to use any well-known spam filter triggering words and it should work fine...

Whenever you put a link in your post, the stupid spam filter is triggered.

And I mean that it's really stupid because no matter how long you've been registered here, how many posts you have published or even if the link is to this very same domain.

link == spam filter

Yeah... the spam filter is stupid. Doesn't allow stuff it should and misses few spam messages every day. It does not learn too because many types of messages are recurring. We have to rethink whether a spam filter is any better than irritating captcha and blacklisted terms. We disabled spam filter on http://dev.ckeditor.com and have less spam, because black list works great. But the same may not work on forum if a variety of spam is higher. We have to analyse this first.

We checked stats and I have to change my opinion slightly - mollom is not so bad. We've got hundreds of caught spam messages every day, so few leaking and few caught hams is not bad. And it can't be surprising that, considering registration without some fancy captcha, if freshly registered user tries to post a link it's caught by the filter. Loosing this politic we may be flooded by spam. But let's see - we'll be testing some settings in next few weeks. Hopefully we'll be able to make filter less irritating.

Anyway, I was also noticed that there should be displayed a captcha if message was recognised as spam. If captcha is filled there should be no problem. Were you asked to read a captcha?