These are the 4 options i got. Plus, how is that person able to spam so fast?
Two options. Either uses macro that has 4 same lines (or more) and clicking it makes it appear like that or he types it once, press enter key, then enter > alt+up arrow > enter and repeat many times. Tho I believe it is a macro.
I guess the Vanila client doesn't have that functionality then.
Might be, I never saw it myself.
For people that have problem with it remember you can use chat commands to do so.
Type in chat /ignore [nickname]
Instead of typing nickname after typing /ignore and a space you can LeftShift+LeftClick a nickname while you have a chat open to make the nickname of person appear in chat. Making it easier to type nicknames of people.
Bigger problem is that Blizzard ignore has only 50 slots per character and that is simply... Hard to survive. And addons only work for chat, don't give amazing function like blizz ignore to never be queued with ignored person upon one team in any ingame activity(rdf, rbg)