I too have seen this bug.
This is an issue with Finder's styling of headers in column view (and maybe other views).
The list interface headers are not "interactive" per-say (meaning selectable and movable), however there is a bug with Finder's styling of the headers for arrange/sort by kind which when rendered incorrectly, makes the headers appear as a regular named folder in the list of files.
Closing all Finder windows and reopening them is not a proper solution, however it does reset the Finder "styling engine" (for lack of time to term it properly) so that it shows the header as a list interface header, and not a folder in the list of files and folder in column view.
I cannot reproduce the problem consistently, however, I often notice it when I have multiple finder windows open, and may even go so far as to tie in the blame with network folder listings in Finder.
I can't verify this but that's my environment a lot of the time.