XEPs current supported are in src/XMPPThread.c, at the IQ disco advertising.

Somewhat implemented XEPs:
    ~ https://xmpp.org/extensions/xep-0085.html
        Only XMPP->Matrix at the moment. Still need to figure out how to 
        get typing indicators as an AS.
    ~ https://xmpp.org/extensions/xep-0444.html
        This allows reactions, which Matrix also has support to. The two 
        systems don't seem *too* restrictive on one-another (unlike some 
        IM platforms I won't mention), so this doesn't sound too bad to do
                HALF-IMPLEMENTED: Removing reacts won't work.
    ~ https://xmpp.org/extensions/xep-0184.html
        Only Matrix->XMPP as of now

For future XEPs:
    - https://xmpp.org/extensions/xep-0421.html
        Using the occupant ID in semi-anonymous MUCs is a desirable property.
    - https://xmpp.org/extensions/xep-0118.html
        Informations on what a user is listening to. Matrix doesn't have 
        good support for status, to be frank. Clients (including KappaChat) 
        should consider having more support for those, rather than it being 
        stuck as a FluffyChat/Nheko feature for the good of the entire 
        federation.
        As such, if _any_ client devs hear this, please consider adding these, 
        (especially if you're a smElement employee!)
    - https://xmpp.org/extensions/xep-0080.html
        Doxxing people over two protocols is great!
    - https://xmpp.org/extensions/xep-0449.html
        Stickers are great. Matrix and XMPP somewhat has support for them, so
        might be a nice-to-have, and also to push over XMPP support.
        A minor issue with that is pack management. XMPP requires a pack field 
        which is used along PEP, it seems, and meanwhile Matrix has ''support''
        for packs too, tracking them is between "annoyance" and "yeah, no.".
    - https://xmpp.org/extensions/xep-0050.html
        Ad-hoc commands that bridge maintainers can deal with XMPP-style are 
        also a nice to have.
    - https://xmpp.org/extensions/xep-0425.html
        As mentionned in #2, moderation _needs_ to be done.

ON STANDBY BECAUSE THESE HAVE BEEN TERRIBLE TO DEAL WITH AND WHO KEEPS WRITING
THESE I WANT TO SEND THEM A NICE, BRIGHT GIFT:
    x https://xmpp.org/extensions/xep-0084.html
        Avatar support would be extremely useful, if just a QoL improvment.
        Matrix and XMPP both have support for these.
        XEP-0084 is a pain in the ass to implement and seems generally just
        unreliable, however.


Not XEPs, but ideas that _needs_ to be added:
    - "GIVE THE PUPPETS APPROPRIATE PLS/ROLES" - Hydro/t4d
      "also it [Bifrost] doesn't respect voice either"
    - Standalone/Static Parsee, ideally as small as it can be(if not as APE).
    - https://www.youtube.com/watch?v=InL414iDZmY


------------------------- MSC LAND -------------------------
- MSC2346: Bridged metadata is useful, at least for other bridges.
- https://spec.matrix.org/v1.11/client-server-api/#third-party-lookups is _very_ 
useful on the Matrix side, to be frank.