That is way too big of a feature to limit because of gilspam. It's annoying, yes, but making new players have to work around so much to contact their friends and remove the ability of a private discussion in-game is not worth it.

That alienates and punishes players for another's wrongs.

I think a chat filter like Guildworks's would be better. People could share their filters online. More effective than simply adding them to a player blacklist, and doesn't punish people who have no business being restricted for a game they're paying monthly for.

Now, as for an option for people to block /tells coming from gc-free players? I wouldn't like it, but that option wouldn't be as bad. New players who really want to /tell someone something who has that blocked can find another method to contact them, ask them to turn off the block temporarily, and then have their /tell conversation. At least it gives both parties their options.

(1000 char limit is hard)