The question Why do I see an "Hiding Questions" message for non-existent tags? notes that if I try to search for a tag that does not exist, like say, this-tag-does-not-exist, and I have ignored tags on that site, I get told that posts are being hidden because of those ignore preferences:
Hiding questions because of your Ignored Tags preferences for tags
This is ridiculous and it is misleading, and leaves the impression that if one searches for that tag and the offending ignored tag one would get results. Instead, one gets results like this one, which simply doesn't make sense:
(Note also that the [homework] tag is part of that query, and it is not in any way expected behaviour to have the results hide posts with the tag.) Compare that search, for example, with looking for posts containing the empty string and those two tags,
which is much more reasonable.
So, feature request:
Don't tell me you're hiding posts when there are no posts to begin with.
The purpose of the banner is to alert you to other possible queries that may yield results that are not being displayed. It is perfectly easy to tell when there are no results to show even with the ignore preferences turned off. If that is empty, simply don't show anything.