Mashable confirmed with Reddit that messages and chat history are no longer available if they were made prior to January 1, 2023.

Retain only half a year worth of content? What the fuck? That's absurd.

In our continued pursuit of empowering communities, we are transitioning to a new chat infrastructure, shared in our previous updates here and here. In an effort to have a smooth and quick transition to this new infrastructure, …

If you can migrate 6 months' worth of data, how is older data any different? The data is there, in the same form. The timespan should not matter at all. It's either the same form, or interfaced to transparently integrate into the existing system - which would allow migration all the same.

A Reddit spokesperson forwarded Mashable a changelog announcement(opens in a new tab) made on June 22 where the company shared that these messages would be removed.

Absolutely absurd.

announcing removal of 18 years of content, of central functionality, announced just 20 days ago, in an obscure place, and after random uninteresting flair navigation and chat channel announcements spanning multiple paragraphs and screenshots.

Baffling.

Acting as if they were managing a personal project that only they themselves use.