It means that the designer may have inserted an unpublished weakness. See also https://en.m.wikipedia.org/wiki/Nothing-up-my-sleeve_number

As in the case of Keccak and SHA3, it doesn't necessarily have to be the designer, it can also be the reviewing committee.

"Glowing" means that it's probably a plot of a government. It's not cryptography-specific.

It's probably metaphorical, to mean distinguishable ?! And the term has never been used in crypto

It's imageboard/IRC slang, you won't find any documentation on it because it's an intentionally obfuscated/dogwhistle phrase intended to only 'make sense' to other browsers who've stuck around long enough to get spoonfed.

Using the term 'dogwhistle' seems like a divisive way to discount what I said. Do you care to articulate yourself in a way that addresses the actual substance of what I said, or is this it?

Agreed that "dogwhistle" is lowkey pejorative. I prefer "shibboleth".

Glowing is not cryptographic jargon. It's a word used years ago by the developer of TempleOS in a livestream to describe CIA operators. He said he could tell who was CIA because they would glow in the dark. Users of the 4chan technology board witnessed this and it became a meme.

To say something glows means to suggest the US three letter agencies are interfering with it. If some cryptography glows, it means it's been compromised by US authorities. Glowies are the operators themselves.