^Of those three, the thread from 2017 has this interesting post: http://talk.qa.collegeconfidential.com/discussion/comment/20761476/#Comment_20761476
This is a very interesting discussion and one I’ve thought about a lot (similar situation to OP). To me it’s not so straightforward.
The advice to only submit test scores if above the published average has wonky implications. Assume that all applicants take that advice:
Some applicants that have test scores above the actual average of all enrolled students but below the average of enrolled students that reported their test scores will withhold them, even though those scores could put them well into the top half of all current students at the school.
Example: A college says their reported average ACT score is 31, with a middle 50% of 30-32. HOWEVER behind the scenes perhaps only half of current students comprise that cohort. Perhaps the lower half averaged 27 and the upper half averaged 31, for a total school average of 29. Using the standard advice a kid with a 30 withholds that score even though s/he is above average for the college.
Every year the average will rise and the proportion of applicants submitting scores will decline. Don't have time right now to prove this but I think it's true.
My questions always revolved around (a) the example in #1 above - i.e. do you submit if just below published average and (b) do you submit if you’re above the school’s average BUT that score is still one of your weakest cards to play (like the situation OP describes).
Considering that the current test-optional situation is unprecedented, insofar as virtually all selective colleges will be test optional for high school class of 2021, I think more discussion is helpful. For whom does this increase/decrease chances, how does this affect the college list, particularly ED apps, etc.