I'm following these directions:
If you are searching using the search box on a question page, you can use
inquestion:thisto restrict results to the post you are already viewing.
Advanced Search Help
I have done this in the past and it has worked. However, right now it is not working and I am not getting the results for the question I am searching from. It's not working on any site I've tried. It appears to ignore the operator entirely, like the operator is invalid (here is an invalid search for comparison).