Purely from my testing (original reason for inclusion of visibility:hidden appears to be weird behavior in old versions of assistive technologies like Window-Eyes that didn't completely remove display:none items from the exposed DOM/accessibility tree), this seem good to me nowadays (from basic testing and experience, display:none on its own behaves correctly in all major screenreader/browser combinations, to my knowledge). /cc @stevefaulkner

(from basic testing and experience, display:none on its own behaves correctly in all major screenreader/browser combinations

agreed.
Somewhat related, you don't need to use aria-hidden=true in combo with display:none :-)

@stevefaulkner

Somewhat related, you don't need to use aria-hidden=true in combo with display:none

are there instances where we do this in bootstrap (honest question, lost track of whether we do or not)?

@patrickhlauke

are there instances where we do this in bootstrap (honest question, lost track of whether we do or not)?

Not that I have seen, but it's out there as advice, due to recommendation in ARIA 1.0, since removed in ARIA 1.1 as it is unnecessary

So we can drop this entirely now? I think we just added it in v3.3.2 lol.

If so, we'll need to remove all our other instances (collapse plugin, etc).

So we can drop this entirely now?

I believe so, yes.

X-Ref: h5bp/html5-boilerplate#1663

Merging this for now so that we match h5bp. Let's punt the aria-hidden redundancy to a new issue.

Opened #16020 and #16021 as follow-ups.