Lemmy.ml is run and was started by the developers of Lemmy. The developers themselves align with lemmygrad, however they try to keep their politics out of lemmy.ml for the most part. It's debateable how effective they are with this, it probably ebbs and flows somewhat.

Moderation without informing you is common across all lemmy instances. Moderators have to go out of their way to notify you, there are no automated messages to go along with moderator action. However, lemmy has always had an open modlog, so you can see why you were moderated if you look it up. Note: sometimes I've had difficulty loading the modlog, particularly the instance modlog (where an overall instance ban would be), though community modlogs tend to load fine.

Also, you should bear in mind the difference between instance admin and community moderators - a community moderator is allowed to run their community as they see fit, within the rules of the instance (like reddit was supposed to be). If a moderator wants to ban you, they may have every right to per the instance rules, even if they have no good justification or you didn't break any rules.

Certainly, the hexbear admin are just as bad as the hexbear moderators, and will throw bans around for dubious reasons while protecting their own committing the same offence. Lemmygrad moderators seem a little less eager to ban, but they're still looking for any excuse. I haven't had any encounters with lemmy.ml moderation though, but I wouldn't consider the place a dumpster fire - that title firmly belongs to hexbear.

One good reason to keep lemmy.ml is simply to keep up with lemmy back-end development.