I'd like a proof to that statement. My arguments, on the contrary are quite simple: the behavior is not documented, the behavior is inconsistent. If that doesn't qualify for a bug, then I don't know what does. If you can prove that the behavior is documented, and that it is consistent, please do.

some of the core Perl5 developers have explicitly stated they believe literals should return modifiable values.

Proof please. Again, my proof is that Arthur Bergman, the person who answered to the bug some 8 years ago, said it's a bug. https://rt.perl.org/rt3/Ticket/Attachment/55414/41707/

I was hoping you'd come around to expressing an opinion or making an argument, but all we got were empty declarations.

I'm sorry, but empty declarations are on your side :) You didn't provide neither proof in docs/code, nor references in support to the claims that many (how many "many" btw? "many" as in "one-two-many"?) devs support your claims. Please, either show hard facts or admit that you have none.

I'm ready to accept your point of view, but you need to corroborate it.