It's hard to know what to make of our past relationships with our NG. They are so significant, and the horrible BD experience we had makes them over heavier on our minds - the scars, the baggage. They are a big part of us and important to understand some of our reactions and fears. But at the same time, how much space should we give these people in our new relationship? How much space should our new people give to our exes? They found someone new and they want to feel special and important, so how much ex talk will affect that feeling for them.
At the moment, I've decided to keep quiet about STBX and D. I had an experience similar to yours with an email while with New Girl. It bothered me for a couple of hours during a romantic weekend. I was a bit absent-minded, but decided not to tell her why. I would only have rehashed my gripes with STBX after all ("it bothers me because..."), not really something interesting to her. A few hours later it was gone and I was happy I didn't mention it. No D or ex talk during that special moment between us.
By the way, does New Guy have a history? Maybe I forgot, but he doesn't seem to bring it up.
Oh and I'm glad NG had text evidence of his caring ways. Like you, I feel neglected sometimes, for no good reason. Sometimes, we need to replay the tape of our conversations and interactions to realize that we were blind or deaf to very clear signals. Sometimes, we need to bull a Buddhist DB, and just acknowledge our emotions without being engulfed by them.
M39 D6 D3 (at S) S 2014-09 D 2016-09
"You can't start a fire sitting around, crying over a broken heart" - Bruce Springsteen.