I wonder if you could make a luhn-like check that would require an additional approval step to post if it comes back positive. Something like "It looks like you may be posting a secret *****. Do you wish to continue?
Of course, then your secret key checker would need to build that string by concatenating so that it wouldn't set off itself.
A project I maintain, Gitleaks, can easily detect "unique" secrets and does a pretty good job at detecting "generic" secrets too. In this case, the generic gitleaks rule would have caught the secrets [1]. You can see the full rule definition here [2] and how the rule is constructed here [3].
[1] https://regex101.com/r/CLg9TK/1
[2] https://github.com/zricethezav/gitleaks/blob/master/config/g...
[3] https://github.com/zricethezav/gitleaks/blob/master/cmd/gene...
Here is a full explanation if you are interested: https://blog.gitguardian.com/why-detecting-generic-credentia...
Something like giving false confidence to the user. Not the best idea.