I always been interested in computer lingo.
In TW folk wanting to HIDE things from the end-user incline to “Read Only” lingo.
I think factually, that is totally wrong.
Rather it is HIDER MODE 
.
Just a comment
TT
Then what is author mode?
Lol!
Author Mode = “A person HIDING what they are doing as soon as they have done it.”
My point? HIDING is essential to meaning.
Regarding the OP I just think the TW lingo about “Reader Mode” is wrong in that the wiki still stays dynamic. And can save.
I merely think “HIDING” is the right word to describe TW in LOCKDOWN 
TT
Eventually we will make a SPOOF LATIN version of TW. Sort of ERA …
TT
Another thing to consider: the phrase “reading mode” could be used to describe a tiddler in which the edittemplate has been closed and viewtemplate is what is viewable. I tend to use ‘viewing mode’, I hope, but it is one more thing to complicate the use of the phrases ‘reader’ mode or ‘read only’ mode.
Maybe ‘Clean read’ or ‘Distraction-free’ mode would be preferable?
Right.
The point being the wiki always remains “live”.
“Read Only” solutions are just “hiders”.
You are correct, I think, to focus on “modes”. But what is it when you limit what is shown? BUT does it actually NEED any explanation??
To my way of thinking the thing end users see is what I intended.
Why ever mention anything else?
Just a query,
TT