I just had occasion to "ignore" another player for the first time, and noticed some glitches:

1. The lobby chat displayed a newline for each line of text entered by the ignored player. These empty lines only manifested when the next line of un-ignored text was entered.
The player was spamming the lobby rather enthusiastically, so this made it hard to follow legitimate conversation and messages.

2. Although the player was blocked from chatting me, he could still challenge me to a game (I don't know if trade requests were blocked, or whether he just didn't think to try that).

Thanks,
Yaron