Going legal is definitely a last resort.
This wasn't an accident though. I believe this was the change that overwrote everyone else's canonicals:
https://github.com/steemit/condenser/pull/3515
Whether you are posting to your own custom, wordpress, steempeak, a nitrous site like palnet.io doesn't matter. What does matter is that you are using a site to publish content that is not steemit.com
Good find on github! Yeah, no accident. We discussed this some days ago, but I don't see mention of one issue I noticed: that even if one publishes on a tribe website, the post timestamp shows that the steemit version is one block before the tribe version.
I hadn't noticed that. That's even more diabolical.