In the ULS search box not-found search queries I found things such as:
- `catala (Catalan; this includes the backtick)
- ´catala (Catalan)
- _體中文 (Chinese)
- ^ppersich (Persian, in German)
- +deutsc (German)
- <kórejčina (Korean, in Czech)
etc.
None of these yielded useful search results, although in theory the search API could be made better to yield the relevant languages.
This is by no means a high priority, because such searches are relatively rare, and people can remove the unnecessary characters, but fixing this some day would be nice.