Slack, Zulip, this feels like we are back in 1999, when the internet was divided by ICQ, AOL Instant Messanger, Windows Live Messanger, and Yahoo Messanger. (Instant/Live was a plus back then). And the only innovation over IRC was a backlog and buddy list. I wonder when the Trillian of Slack+Zulip will come out. I hope Trillian (which still exists) is already working on it.

There have been and always will be competing products and communities that serve similar purposes. We use what we think is the best one. Is this a bad thing?

(Not to mention the fact that Slack is for internal teams, not for IRC-like discussions, though our open newsroom (http://newsroom.grasswire.com) and some other communities (http://fpchat.com) have repurposed it for that.

I think that "best tool for the job" attitude is a straw man. It seems to presuppose that "the job" is per-organisation, or even that there is one job.

In truth many of us believe that the goal is enabling everyone - universally - to communicate without a single body holding centralised control of message history, reachability and access.

Quick review of the globally federated protocols:

  Email is too slow and bulky and lacks "group" capability
  IRC is deeply unreliable and lacks identity, archiving, and media management
  NNTP is too amorphous, slow, and lacks any privacy or security controls
  Everyone thinks SIP is just for telephony (it isn't)
  XMPP is phenomenally complicated yet held great promise
    - if only everyone could agree on the extensions and semantics.
    - but was murdered by Google.

I'm not sure why people claim IRC lacks archiving support. Isn't a bit like saying SMTP lacks archiving support? And doesn't basic IRC always go through a server? So there shouldn't be any technical barrier against a server archiving all chats (private and in channels)?

As for NNTP, I'm not sure if NNTP over TLS, peering with only trusted sites (aka for internal use) would make sense or not. I never did use Usenet much. At least the D language forums have made an effort to bring NNTP into the www era[d].

It's interesting that no one seems to do a decent job of (server side) archiving for XMPP -- partly I think it's because as you state, the XEPs have gotten out of hand -- and partly XMPP appears to be especially popular for users that want privacy -- and treat ephemeral chat as a feature.

[d] https://github.com/CyberShadow/DFeed

(format note, you probably should've just listed the protocols in separate paragraphs, as indented blocks with lines longer than ~50 characters doesn't format very well on hn).