Symptoms
Assume that you create a topic feed that contains a non-English keyword, such as flöwers, in Microsoft Lync 2013 (Microsoft Skype for Business). Then, you send a keyword that matches the feed but has the non-English character capitalized, such as flÖwers, in a persistent chat room. In this situation, the search doesn't display the keyword in the feed.
Resolution
To fix this issue, install the June 7, 2016 update (KB3115033) for Microsoft Lync 2013 (Skype for Business).