In some scenarios, there are bidi neutral characters (such as "?" or "!") in the suffix of left to right title, for example https://en.wikipedia.org/wiki/E! or https://en.wikipedia.org/wiki/Human_Rights_Now!
With RTL interface, either he / ar wikis or enwiki with RTL interface (or commons), writing such titles in the search box looks like "!E" instead of "E!" in the browser (due to bidi algorithm), and this may be a common pitfall[1] for bi-directional users. If this is the case and there are no results, the search backend[2] can workaround such pitfall easily with regular expressions, e.g /([?!]+)([a-z])/ =>$2$1
Notes:
[1] I don't have access to the failed search queries DB, so here is approximation based on wrong redlinks added by editors (not readers) within the article text itself:
use hewiki_p; select pl_title,count(*) from pagelinks where (pl_title like '?%' or pl_title like '!%') and pl_namespace=0 group by pl_title order by count(*) desc;
[2] It may be hard/impossible to handle it in the frontend to properly show [?!] in the end of the query, since there are too many skins/browsers/externals clients