Steps to reproduce (compare two very similar C-files including /* - */ comments):
1. Compare two files A (left-hand) and B(right-hand side) side by side
2. Observe the file B (right-hand side)
The issue: the closing character '/' gets moved to the next line i.e. an LF is introduced between '*' and '/'.
The status of the file B is unchanged, i.e. Notepad++ does not recognize it as changed and these unwanted changed are not saved automatically.
This behavior is, however, very annoying and can very easily produce incredibly buggy and/or unreliable code.