> but communities on open ones like matrix are just as much part of the web as any forum. [...] Would you’ve considered IRC chat rooms on freenode part of the web?
For IRC, absolutely not. IRC (1988) even predates the web (1989). Freenode offered a web-based gateway that ran on their servers, that doesn't make IRC a web protocol.
As for the rest it's slightly fuzzier since in practice they rely on HTTP, but you can't just use a normal web browser to interface with them. You have to run a specialized client that understands the protocol to interact with them. The practicality of the firstparty clients for these platforms/protocols (or in Discord's case the only one you're officially allowed to use) being shipped in a web browser doesn't make the systems "part of the web". The server doesn't give you HTML that you can see in any browser, you make API requests for JSON in a non-W3C-standardized format and interpret it with specialized software. You can't send someone a URL to a message and have them be able to open it in any web browser without additional software.
I am well aware that it's possible to have a link to a discord/matrix message, but it only works if you're already a member of the group and you download the custom software client.
For IRC, absolutely not. IRC (1988) even predates the web (1989). Freenode offered a web-based gateway that ran on their servers, that doesn't make IRC a web protocol.
As for the rest it's slightly fuzzier since in practice they rely on HTTP, but you can't just use a normal web browser to interface with them. You have to run a specialized client that understands the protocol to interact with them. The practicality of the firstparty clients for these platforms/protocols (or in Discord's case the only one you're officially allowed to use) being shipped in a web browser doesn't make the systems "part of the web". The server doesn't give you HTML that you can see in any browser, you make API requests for JSON in a non-W3C-standardized format and interpret it with specialized software. You can't send someone a URL to a message and have them be able to open it in any web browser without additional software.