Hi,
long time no see. 
I was checking Ardour 8 recently (always good to have alternatives at hand and to try new workflows / limitations). I wonder how the current midi situation is after reworking the whole midi concept. While playing around yesterday I stumbled over an old bug, i.e. the first midi note is not played while looping. In my understanding this can´t happen anymore. I can try to reproduce and file a bug report.
The second issue I observed was that Cue point A was not retriggered while looping. When the loop start point and Cue A point starts at the same time Cue A does not play during the second loop. When I slightly shift the loop point earlier it works. So, this is somehow related to the first midi note bug, but maybe has completely different reasons.
Beside of that there was an impressive progress during the last years and I especially find the Cue concept interesting.