Solution: Don't ignore people and don't act like an ass.

-- Lord Tarken Aurelius, the Sage

While I understand why someone would want this, I disagree for several
reasons.
1: Ignore is there to prevent people spamming or harassing you or because you
otherwise have a problem with them. While possible to write bullshit in
broker, it's not really used for that (and I will ban anyone who does that)
and thus broker entries can't really annoy you.
2: You could be interested in an item the ignoree has for sale, and might want
to buy it through a third party.
3: If implemented, people will surely ask me to make a toggle instead,
4: Broker is complex enough without toggles for ingored people. I get
implementation requests for things that already are implemented as it is. I do
not want to clutter it even more if possible, especially with features noone
really needs.

My conclusion is that I will not currently implement it, unless you can find
several people that share your thoughts and can change my mind.