I have added this issue to the tracker:
Issue 2085 – Workaround for specific encoding of commas in filenames (and particularly directory names) by OneDrive WebDAV interface

I'm sending you an email with a development version of WinSCP to the address you have used to register on this forum.

Thanks for your report. I was able to reproduce the problem. I'll look into it.

I'm running WinSCP v5.19.6 Build 12002 2022-02-22

I'm connecting to one of my Microsoft OneDrive accounts using the WebDAV protocol (the only method I've found that will let me connect to one of those accounts) to the hostname d.docs.live.net.

When the folder I upload has a comma in it (like testing, 1 2 3) the folder and contents transfer correctly. When I look at the folder in the remote directory, there is an unexpected folder along with the files that I copied. The folder has the same name as the main folder (in the test case, testing, 1 2 3).

If I attempt to descend into that folder, WinSCP gives me an "Error changing directory to "testing, 1 2 3" error and a code of 404 Multi-Status. If I attempt to delete that unexpected subfolder, I get a 404 Multi-Status error and the folder then appears empty. If I ascend to the parent folder, I can no longer access the contents of the remote folder testing, 1 2 3. If I delete that remote folder, I get a 404 Not Found error and when the parent folder is listed again the subfolder is gone.

All of this is unexpected behavior. Everything else works with the WebDAV protocol to the OneDrive accounts as long as the subfolder name doesn't include a comma.