About [[MediaWiki:Logentry-delete-event/en]]

I still don't get what is the problem with the message text. Either something is visible (=shown) to visitors or it is not.

Yeah, you got it! It is either shown or hidden. But the message does not reveal that. It translates to "X is either shown or hidden" which is exactly nothing said. Anything is either shown or hidden. Not worth to mention. Tautological.

So as as to say something useful, we need to be more specific. Otherwise, the messge makes a nice joke, but does not reveal any information.

I thought that this message is a log entry recording an action, which could either be showing or hiding, so 'changing the visibility' is covering all eventualities. The specific information as to the change is given by parameter $4. So the wording seems to be suitable.