I do not know about you but it happens to me a lot. Whenever I have the WordPress user registry active, let's not say if I allow them to act as collaborators with publication possibilities, there are mansalva records of readers who, later, decide not to participate. And this in the best case.
Because then there are the spammers who register there where they see an ' wp-login.php ' active, to try to strain
And it is especially with these that, although you can erase them, it is better to deactivate them instead of eliminating them altogether. And this is because if you delete it, but if you deactivate it, it keeps your site active for spam, even if you cancel all the permissions, so you do not receive new registration attempts.
This is true in any WordPress with the registry open , and let's not say in WordPress multisite, especially if you have the possibility to create new blogs / sites.
Another situation is when your WordPress site is a community, like a BuddyPress or a Multisite, in those occasions it is especially useful a system of deactivation, temporary or not, of users, in the style of moderation in forums.
Well, there are several simple ways to keep these (or others) users "alive" but inactive …
The first one would be manual action already available in WordPress by default, to download the profile to the Subscriber level, with which they can only read. This, if you combine it with a restriction plugin to access parts of the desktop is practical and effective enough most of the time.
Another option which you may not know, is to use the plugin User Control . What this code does is add a new "capacity" to the user roles through which, and no matter what profile they have, you can deactivate them. The only profile it does not act on is that of Administrator.
Once a user has been deactivated their account is still active but, when they try to access your site, they are shown a message that their user has been deactivated very similar to the typical "baneo" in the forums, and a way to "put hot packs" to users entangled.
The last one, a bit more more sophisticated goes through the plugin Members which you already know. With this plugin you can customize roles and capabilities of users on your site, and even create new profiles.
Here the option would be to create a new profile, which we will call "Bozo" (is a username used in the culture " forera "which indicates that it is an annoying user, and is also used in bbPress), for example. We do not assign to this profile any capacity, not even the basic "Read", which is the only one that has the default Subscriber profile.
Then we only have to assign this profile to the users that we want to deactivate. From there, when they try to access WordPress they will receive a nice error message.
I personally "put" more the "Members method" but it must be recognized that with "User control" it seems less radical, and maybe it enfaden less deactivated users.
Of course, if you can think of a better way to tell it in the comments, there is sure to be and I do not know, and we would all like to learn more.