the existing plugin, jquery.tipsy was deprecated (see 9e712ce6, and T117720).

it was suggested (see T147091 ) that OOjs UI PopupButtonWidget should be used.

however, PopupButtonWidget is severely lacking as a substitute for tipsy. the main deficiencies are:

• no support for hover
• no support for placement, which is practically essential for tooltips (PopupButtonWidget uses absolute positioning)

now, each gadget and script developer can do what @Yair_rand did with Gadget-ReferenceTooltips, i.e., create tipsy's functionality from scratch, but..
(a) there is no good reason to think that such code would regularly be better than tipsy
(b) it makes no sense to force each developer to do their own thing, by removing from the code a module that does it for everyone.

bottom line:
if MW developers do not like tipsy (absolutely legitimate sentiment), they should show restraint, and not deprecate it before viable alternative is available.
until such alternative exists, please un-deprecate tipsy.

suggestion:
the beta gadget "Hovercards" implements all the missing functionality (both hover anbd placement logic, plus all the required pieces from PopupButtonWidget).
I suggest to break the "tipsy" functionality out of Hovercard, provide it as a resourceloader module, make it available to script and gadget developers (including ReferenceTooltips...) and teach hovercards to use this module. (call it OOjs.UI.Tooltip or something).

peace.