Whilie it might have been the right call at the time, much have happened in Rego since then. More specifically, the introduction of if and single line rule bodies makes the extra newline added between each incremental rule feel like it hurts readability more than it helps, as being able to group incremental rules (whether one-liners or not) seems like a pretty good way to make it clear that they belong together.

What I suggest is that this:

allow if user_is_admin
allow if public_resource
allow if user_is_owner

Is kept intact by the formatter, and not turned into:

allow if user_is_admin

allow if public_resource

allow if user_is_owner

While we continue to add an extra newline between different rule declarations, i..e:

allow if user_is_admin
users_is_admin if "admin" in input.user.roles

Still formats to:

allow if user_is_admin

users_is_admin if "admin" in input.user.roles

Note that while the formatter should respect rule "groups", I don't think it should enforce them. If someone prefers to have:

allow if user_is_admin

allow if public_resource

allow if user_is_owner

The formatter should leave it like that.