The lines sometimes "jump" while typing in FakeVim mode. When this happens, the editor window needs to be slightly shrunk or slightly enlargened, presumably until an integral amount of lines will fit perfectly. After the resizing, the current file will be OK, but when you open another file the problem may reappear (requiring another size change).

I reported for the current Qt Creator version that I'm using, but the problem's been there for as long as I can remember. It's really annoying and it would be great if it could be fixed.

In the attached video example, I put the cursor at the end of a line and pressed and helt the right arrow key, while slightly adjusting the editor window size until the jumping stopped.