I know what you're thinking.. hear me out.

I get muted every day just trying to lead BG's or talking to friends because I type super fast with multiple sentences out of habit.

And I don't think the gold sellers spam as quickly as they could anyway. So you could afford to relax it a bit. And if you know the actual allowance duration you could even compare it to a real gold spammer to get the exact number of seconds you could increase it by without them spamming more quickly than they already are, until they catch on.

And consider sending system messages to encourage people to right click > report spammers. Assuming you even use that feature.

OR, reduce the mute time to 30 seconds or less instead of a minute.