It sounds, to me, what you're looking for is something with which you can create a list of people you'd like to avoid, and then be notified if those people show up in your chat / group / raid / whatever.
I'm not a coder, so I'm not offering to help. I've been told that putting people on ignore doesn't keep them from joining a group you have created.
Phanx' suggestion of Badapples sounds interesting, in that it highlights a name, but it hasn't been updated since 2014.
There's an addon called IgnoreMore
http://www.wowinterface.com/download...gnoreMore.html that lets you have more than the 50 blizz allows, include a reason, and it has the same list for all alts. It also hasn't been updated in years, but as far as I know it's still working - I haven't gotten any errors, and people still get ignored.
The author of Badboy just created an ignore addon
http://www.wowinterface.com/download...oy_Ignore.html which I have downloaded but haven't tried to actively use yet, so I don't know how well it works.
Just some more suggestions.
-Barleduq