It is not entirely clear to me what the actual content and quality of these deleted posts is. That you think that they "are of good quality and on-topic (almost all of them have some references, and there is no personal medical question)" is one thing. That the community decision was something different is another thing. As far as I can see, your questions are usually quite well constructed, phrase and researched on the positive side, and very often revolving around "tendinopathy". [Given the amount of time you have spent also on high quality content around that topic I wonder why you are not an expert on that by now that might (self-)answer one or the question on that theme?]
But it looks as if the community decision was mostly: "something is not quite right with the question as is" and therefore the question was
- put on hold
- deleted by the bot with "abandoned closed"?
That means primarily two things:
- A rift in judging the quality of the questions between your perception and that of a number of community members, the actual close voters. (I honestly do not remember if I might have been part of none, any or all of those votes.)
- This is a multi step process that takes some time. At any stage –– and even now –– someone, including you yourself, might edit these questions to address the small or big grievances or problems that were (hopefully) voiced in comments.
I do not exclude the possibility that we/the community might have closed one, some or all of the questions prematurely, unjustly or without adequate guidance on how to rectify the situation (which in principle should be the case in most of the instances?). 39 deleted questions is a frustratingly high number to be sure.
My guess is that "thing 1" would have to be addressed on an individual basis looking at each question separately.
For "thing 2" there are again two sub-problems: first, the community did not help enough by directly editing the question it deemed problematic into shape; but second, you did not enough during the hold-close-delete chain to ensure the survival of the question!
Since I might have the wrong perspective on this situation: as I currently understand the second part of the headline here, I might say that I –– as one of the potential voters on that –– expect a question that was marked as having problems with [on hold] to be edited, voted for re-opening or un-deletion. Once it was delete-abandoned it really vanishes out of any potential focus and help from the community.
One thing to keep in mind is that the delete-roomba operates with a fixed timeframe. That might explain why there is no warning for the OP, as it is always around the same time passed that deletion kicks in. Further you might look with any reputation level at your own "recently deleted" questions. That link for you should be https://health.stackexchange.com/users/recently-deleted-questions/43 or to be found at the bottom of your userpage, tab: questions?
I would like to encourage strongly that this meta question gets at least another answer addressing those aspects I did not understand correctly, left out or overlooked.