I did some digging and couldn't find anti-kick or any similar feature for the most common suspects but it looks like a few people at least already encountered unkickable players/bots so it's not entirely out of the question that it's some new feature they're testing.
It definitely is a cheat or an exploit. I remember in the past that if you use an URL or some special characters it wouldn't be possible for you to get kicked and/or your name on the kick list would appear all mangled up.
BTW, You can use the status command in the console to grab the cheaters/bot id and try to kick them using
callvote kick id
where id is the one your found in the status output
P.S. I think you should link profiles against their steam ids instead of using custom urls which the player can change, making the link invalid.
EDIT: Found some statements by cheat developers from 2019 stating that it's impossible to prevent getting kicked. Somewhat outdated I guess