This feature will affect on users, which are blacklisted by another users.

Until now blocking an user affected, that the blocked user couldn't write messages to the user, which blocked him.
The idea of this extended feature is to make blocked user unable to write in the topics of the user which blocked him.
I believe this allow to reduce spam and attempts to influence, by the blacklisted users and avoid unnecessary actions, by the users which decide to block another users.

To make it more clear here's an example:

User "A" blacklisted user "B". User "B" is not able to write msg's to user "A" anymore and with the extended blacklisting feature user "B" is not able to post in all topics made by user "A".

Suggested and turned away already.

http://forums.d2jsp.org/topic.php?t=46728789

This could be provided for trading ground only for example and exempted from s/a, etc.

That doesn't stop any spam. Might even encourage those blocked people to make threads about you since they can't post in your threads.
and you don't get harassed here unless you act like an asshole in some way.

I see people often post something like "overprice" or whatever in other's threads and then whining when they get spammed.
It's all deserved.

Its not about me or any other particular user, its just about the blacklisting option, which do no good at all. This is only suggestion, but if there's no need to extend it, then let it be, as it is right now.

Bump