Please make search work with special quotes («») used in Cyrillic languages. As of now, if you search for text within those quotes, search will not find anything (both in Thunderbird desktop and mobile).
As an example, empty search results when searching for text in «» quotes without including them:
And when searching for text within «» quotes with quotes included in search field:
Same behavior may apply for other types of "smart quotes" used in different languages, such as ‘’‚‛“”„‟‹›〝〞〟".