So, I'm on your blacklist and, what...I can get rid of you just by sitting at the table? I'm all for it. Honestly, if you can't remember who you hate and why by yourself...

because there are more than 20 player which often play together or play only for best ranking and not for first place, so that no really interesting game takes place..
I can remember these persons today but when I play one week later I do not.

I do not hate these people but its no fun to play with them.

I only want a message that a not wanted person sit in the table..

So, unless you leave, then what? You just want to be more accutely aware of being with someone you dislike? Way I see it, it's either -absolutely- pointless, cuz you'll ignore it and play anyways, or it means one can quite quickly get you out of any game. Especially considering the fact one can sit at multiple tables. So which is it, Mad Max?

Well, after three rounds or so you know when you just can't win the game anymore, so why not settle for a safe 3rd or 4th place? If everyone played aggressivly as you suggest, the game wouldn't be much fun either...

The only thing I want is a message so I can leave the table .. and I will not igore it because I know that the game with this person will be boring.

@aliaiactuasunt: if the persons play intelligent after three rounds nothing is decided.
The point while attack the best is not to play aggressive but to improve your position .. that do not only mean get more fields.. it means get a position to split most of the other players so you may be able to beat them all although they attack you all.. much more tactics needed to win and thats much more fun .. its not killing the best, its shrink him to normal level and improve your position.
But you can not reach this really challenging stage when there people around who playing for second place.

I thought of it again, and there is a point to be able to comment on people you played with, like "plays aggressivly" or "piles up till he's got the 8s". And, if you like, you could write "I don't like him", whatever. Just like the idea of making profiles, especially in the beginning this could be usefull...

After three rounds I can tell you who will not win, even if he's got 2100 rating or won a nobel-prize. So if he's got a nice peninsula, why leave it, rush to (maybe) destroy someone else and get killed?

"The only thing I want is a message so I can leave the table .. and I will not igore it because I know that the game with this person will be boring. "

So, one could get rid of you easily. Sweet, I'm all for it.

Ah so you complain that people go for the best ranking instead of position nr 1? ARE YOU KIDDING ME! I remember you having 1 country left and you asking me "if there could be an alliance". So you the same as the people you dislike. Sounds to me like you suffer from a split personality.
Love yourself buddy, love is the answer!

This sounds reasonable (of course not everyone would use it), and aliaiactasunt's generalization of it makes a lot of sense.