Safewords have an obvious reason for being there and they should most definitely be known by the Dom/e and ofcourse he/she should stop if that word is used. If he doesnt well then he/she isnt a good Dom/e imo.
On the other hand online play is much safer and you as the sub can always choose not to obey or just stop or put the person on ignore or tell a moderator.
all logical right?

I trust my sub to tell me if I go to far and if she doesnt well then there is a trust issue tht needs to be solved first.