You know what? I actually believe Valentine when he says doesn’t want to kill Jace. And for me, that is exactly the problem. This is another instance where Cassandra Clare could have genuinely made Valentine scary and once again she whimped out.
First of all, Clare wrote Valentine actually showing concern for Jace. And Clare actually made Valentine sound genuinely concerned. It really not adding anything to Valentine’s street cred. And Clare could have very simply corrected this by having written Valentine killing Brother Jeremiah right in front of Jace. This would actually be Clare showing us instead of telling for a change, but again Clare won’t let us have nice things. *sigh*