What changed in each stable point release?

Is there a way to easily see what functional changes and/or fixes are in a discourse point release ?

Did you try The releases category?

Yes - but I’m looking to find out what’s changed between 1.5.1 and 1.5.2 for example.

Short Answer GitHub:

And if you are on 1.5.1, you should upgrade to 1.5.2, as it seems to be all security fixes.

Yep, the policy is that updates on the stable branch are only (a) security fixes or (b) high-profile / high-impact bugfixes that have already landed in master for a bit.