With a view to producing a match with a database string that includes diacritics, RompR seems to need the diacritics to be present in the keyed in search string. It would be more convenient to enter a word without caring of diacritics. The match could actually be tested against database fields filtered out of their diacritics. The python unidecode module is pretty good to this job.
Unlesz you are using the "Search only in Music Collection" option, the search is performed by MPD/mopidy, so this is not an issue with RompR
When searching in my local collection only, or everywhere, the issue occurs, as shown below with a simple example:
So it looks like you're using MPD, the "only in music collection" option is only available for Mopidy and is not present for you - therefore MPD is doing the search, not RompR. RomoR is merely displaying the results that MPD returns.
I suggest you try a different MPD client. If that produces the same results then this is an MPD problem.
I checked the MPD code and it appears that MPD matches strings as they are (both the search string and the tag string). So, the MPD client won't make any difference. This is an MPD issue, indeed.