Suggested

Block people in chat

Hi, I’m currently in a league that is having problems with a particularly nasty and disruptive player posting some really offensive content in league chat. Can we please have a Block button in league chat to block these comments or better still anything posted by a particular player. Thanks

As far as I know, the league host has the right to delete any posts, by anybody, in the league chat.  It may be easiest to contact your host and request that they delete any subsequent posts of such a player, of the same nature.  The host could also boot this player from your league if this behaviour persists.
This is the sort of behaviour that should not be tolerated in the first place...

The host must have the right to prevent the player from writing in the chat.
I've encountered players who clog the chat.

That is when, I, as a host would hit the ban hamner...

This particular player gained access to a friends Google account and spammed some unpleasant  stuff using multiple accounts. He was banned by the league host but came back again on another account. 3 days of bedlam but I'm not convinced he won't return.