Else-net, there was a theory put out that if one feels marginalized already, then the perception of "Stack Overflow doesn't want my question, they down voted it because it lacks any code" is evidence of that marginalization even though its directed at everyone.

This seems likely. If you are mistreated for a given reason, you would likely attribute mistreatment elsewhere to having the same cause, and given that would be ones first impression of mistreatment, even with evidence that the mistreatment is for another more broader issue, people will likely contribute the mistreatment to the original reason they were mistreated in the first area. It is similar to making a bad first impression; it takes a lot more effort to correct a bad first impression than to maintain a good first impression.

With Stack Overflow, its also important to remember the 0th impressions of people finding the site through google.

Finding material that is off topic but preserved for some reason is often cited as a negative experience. The "I searched for XYZ and it was closed as not constructive" (note: not constructive hasn't been a valid close reason for several years).

This brings up the question of "should that material be findable on Stack Overflow if people are having such poor experiences when finding it?" and "are people finding the closed questions of yesteryear a disincentive to participate today?"

The finding things closed as a duplicate sign post isn't working as intended with redirecting them to the proper question - because when there is an answer to the question (that may or may not properly answer it) it prevents the logged out user from getting redirected to the duplicate.

You got this exactly wrong:

The negative experience is that the interesting/useful questions/answers aren't rewarded.

It's bad that they are closed with harsh and false ("not constructive" on some of the most useful question there was...). It would be even worse if they were entirely removed so we couldn't find the answer.

Being treated exactly the same as everyone else is concrete evidence of non-marginalisation, in my book - and what everyone claims to want