We know that when you polymorph in D&D 5e, per the spell, you lose access to your class features, as discussed in this question. However, polymorph does not say it cancels on-going effects on the target.
My specific question is: If a raging barbarian is subject to polymorph, does their rage end or continue?
On one hand, Rage is a class feature, which suggests that it ends when the barbarian is polymorphed. On the other hand, Rage essentially applies a status effect to the barbarian with conditions which specify when it ends, which suggests that it might continue while polymorphed.
I am aware that Jeremy Crawford has tweeted that the answer to this question is that the rage ends. However, Jeremy Crawford also rules that the opposite is true for Arcane Ward, another class feature with an on-going effect. If your answer is "Jeremy Crawford is right", then please also explain what components of the effects determine whether it is retained during rage, so as to clarify the apparent contradiction in Crawford's tweets.
I am also aware of this similar question on the Bladesong feature, although that is a different feature to Rage and Rage is probably a more common scenario, so I thought I'd bring it up separately.
Best Answer
Rage ends when polymorphed. Arcane Ward is the odd one out: it's not part of the creature's own game statistics
Jeremy Crawford was actually asked this exact question, and gave this answer:
Essentially, once active, the Arcane Ward exists as a separate entity. This is reflected in the language used when describing its ability to absorb damage that the wizard takes:
The ward is clearly described as a separate entity with its own pool of hit points and its own behavior for what happens when it reaches 0 HP, etc. This is in contrast to temporary hit points, or maximum HP increases, which both affect the creature directly.
So, the answers you have linked already explain why, in general, class features like rage and bladesinging go away while polymorphed. This answer explains why Arcane Ward is the exception to that rule.