well if your objective is "never see a spam msg ingame", the solution should be as fast as they create an acc and get back to spam, i mean, go stop playing, send a report wait some days .... for 1 spammer in those days u will get trilion of new spammers operating, it should be a quick and strong solution to the problem.
disable class chat for players lower than lvl10, at least we keep our class chat clean, they can teleport and use general but its not annoying as create lvl1 and talk to all the "mages" while u trying to block last bot.
remove that 30 sec penalty for players over a certain high lvl, make no sense.
add some sort of temp chat ban if u get reported for spam from a X diff users.
add captcha verification until a certain char lvl, to get ride from mage bots, so u lower the gold income those company gets.