To use this you'll need to disable Nexus chat in the window you want to customize and make sure that the Realm channel is enabled (it's what the allowed messages come through on, Nexus orange color is retained). I like to keep a separate chat tab with Nexus chat enabled so you can get some context if you need it for some messages. Currently only works with Nexus chat. I may expand it to other channels if there's interest.
Use /cfilter to bring up the list of keywords that will let a message through. You can add and remove them as well. Any message on Nexus chat that has any of the words in the list (case-insensitive) will show up. All others will be blocked.
This was made because I couldn't stand the Nexus spam and then developed it into a real addon so other people could use it. Will probably be making it better over time.
Let me know of any issues or feature requests here: