Most new people need help and this can be the best place for them to reach out for it.
The board should not have to be restricted to those potential players due to the handful which may be problematic.
When I look at the BBS, I easlity can make up the number of PNG's / locked threads a certain forum generates. Who knows, maybe someone has a stat on this.
If these stay public, 1st they do is put bad advertising on AH, 2nd they do not contribute to the game nor the forum.
I wonder how many threads you have locked in Help & Training ( a place where a new customer SHOULD look ). Oçlub and General discussion should be members only, like 200.
I would not call it restricted, I would call it new customer protection.
Would save you a lot of time