1 Go to some editable page (or create new one).
2 Enter some mark up.
3 Look preview. All ok.
4 Switch to MARK UP again an type here some path with folder names begining from "_" symbol. For example:

C:\Folder1\Folder2_Folder3_Folder4_Folder5\filename.txt

5 Switch to PREVIEW and found some missing slashes:

C:\Folder1\Folder2_Folder3_Folder4_Folder5\filename.txt

It is very inconvinient.