I generally don't put players on ignore, but sometimes I ignore most of what they say.
Recent Example: Player X advertised in LFG channel that she was looking for more players for a task force. I replied directly to her, which I have done a million times to other players, "Can I join your Task Force?"
Her response, "That's why I was advertising it."
Now, you can read that multiple ways - bitchy, or jokey.
Turns out, she had a bitchy message for another player almost as soon as we began the first mission. I didn't put her on Ignore, but I didn't bother to read most of anything else she wrote throughout the task force. I was there to have fun, to play my favorite game, and in case Player X wrote something that I needed to read ("Team Transport to the next mission" or "Stealthing to the end of this one" etc.), I didn't have her on Ignore.