Title says it all. A number of issues occur if you try to remove anyone from the ignore(I sometimes, or used to, use it occasionally to temporarly add someone with the intent of removing them from it later);
Local chat is more likely to stop working for no reason.
You still don't see local chat from the individual you removed.
They get added back to the ignore by the client or server the moment you log back in.
While there are people I likely won't remove(specifically trolls), there are some I have tried repeatedly to remove and have been unable to. Just using remove ignore doesn't work :/.