I'm happy to answer the technical criticism expressed in the blogpost relative to Jabber. Disclaimer, i'm a Jabber user and i'm a volunteer for the newborn
https://joinjabber.org/ project.
> server implementation
In the Jabber ecosystem, there's a bunch of servers. Prosody and ejabberd are the most popular ones with easy configuration and extensibility, high reliability, support of all modern features (XMPP Compliance Suite 202X), and packaging for all distros. There's a lot more servers, but they may not be as reliable/complete.
> use matrix.org (...) or (...) will it be up (...) ?
There is no equivalent in the Jabber ecosystem, on purpose. Nobody wants to centralize all accounts, or wants to advertise services which may disappear some day. Jabber services, like web hosting and emails, is meant to be provided by hosting providers which will still be here decades from now. As with any protocol, you should never trust a provider of a single service (who doesn't deal with other protocols), unless they're the person developing this service and you want to support them. More often than not, these single services hosts are run by inexperienced volunteers who cannot guarantee they'll still have time and motivation to maintain the services years from now.
Some non-profits have been serving Jabber accounts for their members for more than a decade, like JabberFR here in France since at least 2005. And these "small" servers (JabberFR has ~700 parallel users and 2-3K servers federated with) take very limited resources and have much better uptime than most commercial messengers.
> Voice and video
This has been a long problem in the Jabber ecosystem because little people were working on it. Nowadays, 1-on-1 audio/video works perfectly across Conversations (mobile) and Gajim (desktop) and group AV works perfectly with Jitsi.
> Matrix is so hard to set up on a server
Jabber is really easy to setup on any server.
> Encryption isn’t mandatory in Matrix
Encryption isn't mandatory across the Jabber ecosystem, though some clients strongly encourage and facilitate it. This is the only criticism of matrix in this blogpost that equally applies to Jabber.
> How does the average person curate your list and avoid choosing a server that will be offline pink in the future?
That's a fair question. Registering with a hosting cooperative (not private corporation) which has a good track record is a good start. This is one of the reason we started the joinjabber.org project. Though we don't have a lot of servers recommended there just yet, we intend to curate services according to public criteria in the future.
> directing friends & family towards Signal is less of a cognitive burden
Not in my experience. This leads to questions like how can i talk to someone who doesn't have a phone number (you can't). Why is the service not working sometimes (smaller hosts have better uptimes). Why am i receiving phone calls from weirdos who took it from a groupchat i joined, i thought signal stood up for privacy. And hypothetically, in the future: why is Signal actively cooperating with law enforcement in my country. Why was Signal sold to a data-mining private corporation. Why is Signal going bankrupt and closing all services and where can i go...
I'd much rather take 5 minutes to explain to someone that Jabber is like email and they need to find a trustworthy, reliable provider, than spend hours and hours dealing with the mess and pain a centralized approach like Signal creates. Source: most of my friends and relatives are on Jabber; some have some moderate complaints about UX but it "just works".