Thanks for bringing those to my attention.
Pavatar looks pretty dead. The page has a date of 2006 for the “latest spec”, and the latest post on their support forum is from 2008! And I’ve never heard of it until now. This does not bode well.
As for Libravatar, it says:
How is Libravatar different from Gravatar though? The main difference is that while Libravatar.org is an online avatar hosting service just like Gravatar, the software that powers the former is also available for download under a free software license.
Why would you want to run your own instance? Our belief is that centralised approaches don’t put users in control. If you own your own domain name, you control how mail is delivered to your domain. You should also be able to control how avatars are served to other websites.
For example, if you own a business, you may want to integrate with existing systems (e.g. a staff directory) and delegate authentication to what you’re already using (LDAP?). Plus, you can choose what happens when email addresses are not found (display your company logo?).
So this is an additional layer of complexity. Rather than Discourse being the single point of truth for avatars, there’s another service you install alongside it which is…
I dunno, I think merely serving avatars is not that useful of a service to run, the difficulty of spinning it up is not worth what it provides to you versus Gravatar.