On the deadnaming and related issues, it would be interesting to create a webmention mechanism for the h-card portions so that users might update these across networks. To some extent Automattic’s Gravatar system does this in a centralized manner, but it would be interesting to see it separately. Certainly not as big an issue as deadnaming, but there’s a similar problem on some platforms like Twitter where people will change their display name regularly for either holidays, or lately because they’re indicating they’d rather be found on Mastodon or other websites.
The webmention spec does contain details for both editing/deleting content and resending webmentions to edit and/or remove the original. Ideally this would be more broadly adopted and used in the future to eliminate the need for making these choices by leaving the choice up to the original publisher.
Beyond this, often on platforms that don’t have character limits (Reddit for example), I’ll post at the bottom of my syndicated copy of content that it was originally published on my site (along with the permalink) and explicitly state that I aggregate the replies from various locations which also helps to let people know that they might find addition context or conversation at the original post should they be interested. Doing this on Twitter, Mastodon, et al. is much harder due to space requirements obviously.
While most responses I send would fall under fair use for copying, I also have a Creative Commons license on my text in an effort to help others feel more comfortable with having copies of my content on their sites.
Another ethical layer to this is interactions between sites which both have webmentions enabled. To some extent this creates an implicit bi-directional relationship which says, I’m aware that this sort of communication exists and approve of your parsing and displaying my responses.
The public norms and ethics in this area will undoubtedly evolve over time, so it’s also worth revisiting and re-evaluating the issue over time.