IF E.P. post as ER, that is going too far.
That is something that just should not be done.
If he was joking or something, and made it clear he was E.P. and not ER, then that would be different. But I thought it was ER posting.
If E.P.was posting as ER is what happened, E.P. needs to apologise to ER and then go sit in the corner.