The impacts of the environmental damage are not necessarily worse than the environmental damage from not sinking superyachts in the long term, if it becomes a common enough threat that rich people no longer feel secure in owning them.

The concern with anything too destructive is with the property and safety of workers on board imo, not the ships themselves.

I’d recommend Andreas Malm’s book How to Blow Up a Pipeline if you want to hear more about the reasoning for this sort of thing.

You cannot do that with other social media.

Facebook likes, Twitter likes, Discord reacts, LinkedIn reacts, etc. are all publicly visible. The only possible slight difference with this is that in some cases people might not be aware, in which case the issue would be that it is less obvious to a casual browser than Facebook’s “AncientMariner and 23 others liked this post” rather than that the likes are visible at all.