Yeah..
Even nice wannabe masters (like me I like to think) can do some awful without intending to do any harm.. (or it could be someone that isn't nice if you don't know him all that well)
The human body is more fragile then people might thing so don't take any chances..
(not that I know all that much about this but..)
Personally I've put "getting to know my local bdsm community" on my todo list (for whenever I start living at a place where there actually is an community)
That'll allow me to learn a bit about this stuff as well as allowing someone in the community to evaluate how I'll handle it or possibly don't handle it..
Not sure if that is the normal way of doing it or not, but it's the only think that sounds reasonable to me..
Do you know if your online dom have been active in the community in any way before?
Perhaps someone he's been involved with before (if there's someone) can tell you a bit about how he is when doing this?
Well, going to quit rambling and go and get some sleep now..
Good luck