I'm aware of the limitations, as far as I remember it has to do with the sqlite full text search which is used for the collection.
I plan to get rid of SQL-based search for the collection entirely which means rewriting parts of the collection model and search, which I started on a few years ago, it should get rid of these limitations also. When that is done, the collection search will be similar to the playlist search, search will use a model/proxy and not SQL.