A simple way to stop the spam a lot of the spam is not allow gold to be tradeable from other people for a character lower then a certain threshold. Stops all the cross realm service boosts.
Another way to also clear up chat is to support it by creating a boost lfg section, where they can list just services and ban advertising of services within chat.
They stil clog the group finder.
Trade chat is just a bonus.
After all these years when i was geting nice whisper from certain wanna be gms i am hoping that these boosting services next step would be whispers. That would be the chery on top.
But no mater how many times i do it never ends.
So it needs to somehow get filtered away, the way i am doing it with badboy addon for trade chat…
In my opinion this is a big issue and stress for me, same as the damn mass guild invite addon whispering and inviting me just because i am not in a guild inviding my privacy. (But thats a different subject).