As mentioned in a single thread I think you can keep adding messages without effecting the response rate of the other person if they don't reply , but if you start a new thread each time then the other person will be slowly given a lower and lower % return score! does it matter, if scouting for an option reply rates 10% Vs 90% might influence choices,
I doubt if the set up here is sophisticated to recognise that a member is emailing themselves (i did this back in the day as I too wondered if messages were going astray such was the poor response!) if you don't reply (to yourself) your score will possibly go down, do reply and score could go up! Send yourself 100 messages to improve your rating If i get the time I'll try it!
I see an EBay for sale option coming soon, along with 10 positive feedbacks £15, close some ones account £25 and a full set of decent unique profile pics £50!