[Standards] Remove requirement to send disco#info feature in XEP-0030

Dear community, it's been a while I spoke up here. I would like to discuss the removal of the following part-sentence from XEP-0030 (in Final status!): Announcing that feature is redundant: An entity which replies with a properly constructed `<query xmlns="http://jabber.org/protocol/disco#info"/>` element is bound to (and has always been bound to) have implemented XEP-0030 to the best of its knowledge. As this is a Final(!) status XEP, here is my estimate of the impact this change has: - Implementations which required the presence of this feature on the receiving side would now become non-compliant: They might assume that the remote entity did not really support XEP-0030 and fail with an error. Such implementations would need to be adapted in order to be able to interoperate with implementations which follow a revised version of XEP-0030. I don't see any other impact. I also strongly suspect that the set of implementations which follow XEP-0030 to the letter is rather slim (I only know of a single one, which would be the Rust XMPP library xmpp-rs [1]). The reason why this came up: There have in the past been cases ([2] and another, not-yet-filed issue against Prosody IM where the disco#info feature is missing from MUCs) where implementations didn't emit this feature. The seeming pointlessness and lack of information conveyed by this feature var make it easy to overlook and low-priority to fix. The fact that this has gone undiscovered for at least one Prosody IM release cycle further supports the assumption that the number of implementations which rely on that part of the spec is rather small. Your input is welcome. kind regards, Jonas Schäfer (these days without "special" role in the standards process) [1]: And there exists at least one fork which removed that check: https://gitlab.com/nesium/xmpp-rs/-/commit/1ddb050 [2]: https://issues.prosody.im/1664