alt Hacker NewsWait, this statement seems way too strong.
The linked article points out that Datomic doesn't support branching from the past. It absolutely does support branching, and I've built entire test suites that way.
From a cursory glance, I'd say Datomic does exactly what the original parent article is discussing. It works great and it's super convenient.
If each "branch" is read only, it's not a branch at all. The entire idea of branching implies that you can make changes on one branch, then switch to another branch and make changes to it. They start from the same point and grow in different directions, as the metaphor of branches on a tree depicts.