I have a file with a single Unicode character in it: π― (Unicode character CANDLE, codepoint 128367, #o372557, #x1f56f).
When I open this file via emacs -Q and hit C-l, the display buffer has issues. Namely, the character becomes invisible on that line, and instead somehow appears in the menu bar line (the top 'File,Edit,etc' menu bar line disappears). It's like the whole display gets shifted up 1 line. If I move the cursor left, I can see the original character, which is now being displayed 2 times in the buffer despite existing in the file only once.
In practice, this makes it very difficult to edit files that have unicode characters in them. For files that have many lines in them, this issue results in lines being visually duplicated. Selecting them via C-SPACE does fix the display issue, until I start navigating around the file again, which triggers the issue.
System: WSL2 running Ubuntu 20.04 on Windows 10
Emacs version: GNU Emacs 26.3 (build 2, x86_64-pc-linux-gnu, GTK+ Version 3.24.14) of 2020-03-26, modified by Debian
emacs -Q(no init file), then consider reporting an Emacs bug:M-x report-emacs-bug. The problem might be due to WSL2, but the Emacs developers will likely be able to tell you whether there's an Emacs bug here.-nw)?-nwdoes not fix the issue. I've just reported it to the emacs bug mailing list π