List of steps to reproduce (step by step, including full links if applicable):

• Have the reply tool enabled
• Go to this page: https://en.wikipedia.org/w/index.php?title=User_talk:Usedtobecool&oldid=1073290824#Merry_Christmas_and_Happy_New_Year
• Click on the reply link

What happens?:

• The reply tool link becomes disabled, as to all other reply to links on the page.

What should have happened instead?:

• The reply to input box should open an accept input.

Software version (if not a Wikimedia wiki), browser information, screenshots, other information, etc.:
Reloading the page resets the status, and makes other reply tool links work on that page, but not the offending one.

Console error reports:
jQuery.Deferred exception: can't access property "ownerDocument", sibs[0] is undefined

Similiar to report in T301427 , though this is failing even without the Beta "new video player" being enabled.