So to start here, Mr Coren is questioning his own behaviour which is good. He has then agonised in that way people do, when crimes come into focus, with the logic that goes "if there were no guilty people then innocent people could not be mistaken for guilty".
This is true as a concept but wrong as a concern. For all crimes there are perpetrators and in each case we need to put the appropriate effort into identifying them to protect the victims. Society has no other choice if it is to be civilised. The same effort though should also protect the innocent with at least equal care.
If employee A puts two "x"s at the bottom of an email to employee B and employee B complains, then employee B should be told "this is not an issue". At the same time employee A should be advised to stop adding the "x"s to their emails to employee B, simply on the basis that any colleague should stop any optional behaviour which another colleague finds disturbing.
Mr Coren's concern is naive, self-indulgent and stupidly disrespectful of the alleged victims in this case.