Since zefklop's commit of https://github.com/reactos/reactos/commit/0c13ff2a4b3673cac8e70ca45139febc4114f568 we have a double/mirrored cursor in the line number column of notepad++.
I believe that this is caused by a StretchBlt flip needed in the replaced code. I have created a HACK patch that improves the outcome and makes it look more like what we see on notepad++ when run on Windows here: dib1bpp_c_improve.patch
See the results of my patch here:ReactOS-15-2246-Patched.webm
In both the old and new cases we have a white dot that follows the cursor in the top left corner of the cursor's working area that I do not understand at all.
Maybe a developer can use this to make our notepad++ look more like the one in Windows.
New patch that fixes the extra top left dot is here: dib1bpp_c_improve1.patch.