Mipbar,
I just tried it and you're right, this is not working as expected in the latest build. I'll open a bug.
There are two other ways to remove the permissions in PFDAVAdmin, and they both appear to work properly.
One way is to use an import file. You can run an import where every line looks like this:
SETACL<tab>Public FoldersFolderA<tab>SomeUser<tab>Remove
During import, when a role of "Remove" is encountered, that causes the removal of any permissions for that user on that folder.
The other way is to use a Custom Bulk Operation. In this case, ti's pretty simple to configure it to do what you want. Here are the steps:
1. Go to Tools -> Custom Bulk Operation
2. For the Base, choose the Public Folders root or the selected folder, depending on what you want.
3. Hit Add, and choose Folder Permissions as the operation type.
4. Hit Select, leave the first permissions dialog blank and click OK (since you don't want to add any permissions), but in the second one add the user who you want to remove and click OK.
5. Now you should see that back in the Folder Permissions Op window, it shows the user you've selected followed by "Remove".
6. Click OK and it will start the operation.
You can use either of those methods as a workaround until this bug is fixed.