In OPAC, searching for anything, and then limiting the search with one of the facets from the list in the left side of the screen -> the results page shows no indication the facet is used limiting the search. (Other than having a cryptic "su-to: foo" - this does NOT help the normal patron!) Ideally, the facet(s) in the list to the left side that are chosen to limit the search should be displayed differently from all the other facets.
I think bug 10857 is what you are looking for. *** This bug has been marked as a duplicate of bug 10857 ***