By the way, I'm running Chessbase 14, version 14.18, Jun 4 2018. In case it's relevant.
Chessbase search

I'm glad you let know this happens in your CB, too.
Just to be clear, exactly what version of CB are you running? It's under File -> About.
ikalel

OK. Just to let you know, you can get around that by searching for the online-player-like name in the search box under the Players tab! And it will find it.

Of course, you can always get your db download with online player names and switch each and every single name to start with a capital letter. Just like the official Chessbase databases and it should work.
To all Chessbase users:
I'm searching for games in a database of online players, that is, players with names which are not capitalized, for the most part.
I open the database, do Ctrl+F, and put in, let's say, superstar, and the search returns nothing even though the database contains about 10 superstar games.
After I reopen the search mask with Ctrl+F I see that "Superstar" is already prefilled NOT "superstar".
Why is Chessbase auto capitalizing everything? I want to search for superstar (the player's nick) and not Superstar.
P.S. I noticed that in Chessbase's official databases all names are capitalized - even names which are not supposed to be capitalized, such as von Bruehl.