Quoted text with horizontal line becomes level-1 heading

Reproduction Instructions

Write a comment on a Phabricator task like the following:

Some text.

Try anything.

------

EDIT: It seems to be different.

Then quote this comment and observe how the second paragraph became a level-1 heading.

Live example at https://phabricator.wikimedia.org/T227699#5837193.

Phabricator/Arcanist Version

phabricator
    82a0d4251ae61e2387d9e4abc17992db8c9e40db (Wed, Feb 12) 
arcanist
    ccfb01e19255b204731f7d71264337e16b3a9d02 (Dec 11 2019) 
phutil
    b6f4e8e0f9958a5b9818200d70fae5e4512569a9 (Tue, Feb 11) 
sprint
    7f34f377a425e0a53504355e991d9ccf4eb40de6 (Aug 23 2018) 
security
    858c719110eb13a3c4e31262edc7a340c0125f8a (Aug 16 2019) 
wmf-ext-misc
    7826f333ffb246632774bbbe5c02a1887db4c877 (Thu, Feb 13)

I can’t immediately reproduce this, and expect it was fixed by https://secure.phabricator.com/D20965.

However, since 82a0d4251ae61e2387d9e4abc17992db8c9e40db isn’t an upstream version, I have no idea if you have that patch or not.

Here’s what it looks like on master:

Can you maybe provide the exact input text that isn’t working and I can see if it reproduces? It’s possible my reproduction case isn’t accurate and there’s still a bug.

The exact text I used was:

>>! Elsewhere, such-and-such...
> Some text.
> 
> Try anything.
> 
> ------
> 
> EDIT: It seems to be different.

Ah, didn’t realise we diverged again momentarily. Per https://phabricator.wikimedia.org/source/phabricator/, looks like our last upstream pulled was 46fcd135ae68 (3 Feb 2020), which is from 1 day before your fix.

Using the raw remarkup from https://phabricator.wikimedia.org/T227699#5882123 in a comment preview on secure.phabricator.com, I cannot reproduce the issue:

Ah, great. Let me know if you’re still seeing issues once you pick up the patch.