Undocumented change in binding of buffer-local variables?

[Luc Teirlinck]

There used to be (in Emacs20.7 and earlier) a problem with binding a
buffer-local variable with let and then exiting the let form with a
different current buffer.

>From experimentation, it would seem that this problem is now totally
solved.  Is this correct?  If so, would it not be worth mentioning
this in the GNU Emacs NEWS?  (Maybe I overlooked something, but
conducting a search for "let" failed to find anything related.)

I found a bug in ielm which I can easily fix and for which I will send
a report and patch soon.  However, the best solution depends on
whether or not it is now safe to exit a let-form, binding buffer-local
variables, with a changed current buffer.

Sincerely,

Luc.