[Design] Localizable tooltips, for html form fields - guidelines?

[Nick Wilson (Quiddity)]

I've asked a few questions at
https://phabricator.wikimedia.org/T95076
that someone here might be able to help with, namely:


1. What accessibility issues need to be considered, for using tooltips
in form fields? (e.g. old browsers, screen-readers, accesskeys)
2. Do we have any mediawiki guidelines on what developers/extensions
should use? (and should they be linked in the Living-Style-Guide
<https://phabricator.wikimedia.org/tag/living-style-guide/> e.g. here
<http://livingstyleguide.wmflabs.org/wiki/Inputs> or is that outside of
it's remit?)
3. What is the best external documentation, and "best in class" examples?
4. Where do we currently store some examples? e.g. the title="Enter a
short summary [Alt+Shift+b]" in enwiki's edit-summary field.
5. What pragmatic limits are there, on the formatting & length of
tooltip content? (can we do split lines in basic HTML? How much harder is
it to get clickable links in them? F108798
<https://phabricator.wikimedia.org/F108798>: this is very pretty, but
the rendered HTML is gigantic, and it's still not clickable/copyable text.)
6. What other things should I/we be asking?

Answers over there, please and thank you. :)