I am able to delete a user from Users and Group but when I search a user name in Contents/users folder and then try to delete a particular user it shows me the following error
Failed to delete items: 1 could not be found
This happens to other actions also like copy rename etc
Personally, I would suggest you document your "right" way/path to delete the user: Delete a user from Users and Group. So it could be shared with ur team, I supposed you are the admin role/team in ur company. Document and sharing would be always valuable and helpful.
Just a quick idea: If you look at the path: admin>Site Setup> "Users" and "Content" are even belong to the different components. I don't think it's really designed for "user" edit, by now it's more about a quick path to "show" by the "folder" of "Users". And considering the security issue, you can't really just delete them like other items listed in "content".
@tisto Feel free to give ur comments or correct me.
In a Plone 3.3 site taken over from someone else I had a similar problem that I solved by reindexing portal_catalog (if I remember right)