On 2/2/2025 10:56 AM, Udicoudco wrote:

> Even though this change is less disruptive, there might be more
> concerns about backwards compatibility today than three years ago, if
> this is the case a new value to \matheqdirmode can be added.

I checked how I'd do it in luametatex and  noticed a potential issue
with the patch: because there can be more than one node (par plus plenty
dir) you need to flush the list starting with vlink(head), otherwise you
leak nodes.

(Because pop_nest is kind of dumb that should be enough but in other
situations one should also set tail to head and the next node of head to
null.)

(I actually added a bit more clever variant so that i can test some
scenarios, but right now I can't forecast side effects as i have no clue
  about intended usage in macro packages as we don't need it in context.)