Requested feature overview description.
This feature would allow for artists who are trying to showcase their SFWs without worrying that their fans may end up on e621, as opposed to e926.

As e621 features NSFWs publicly without having to sign in, fans of the SFW artist may unknowingly end up on an +18 site when searching for the artist's name.

If the artist could be hidden from e621 and only featured on e926, Google wouldn't index and redirect their fans to e621.

Why would it be useful?
Useful for SFW artists trying to avoid being indexed with e621 via Google Indexes.

What part(s) of the site page(s) are affected?
https://e621.net/post/index & https://e621.net/tag/index (in relation to Google Indexes)

If this were implemented, something would have to be done to the artist pages as well. Either the NSFW and SFW artist entries would have to be kept separately, with the SFW one manually scrubbed of any references or links to their NSFW work or name, or the e926's version of the artist index would be modified someway in order to hide the NSFW references and links.

I don't think that's easily doable. We'd need separate aliases and implications for e621 and e926, as well as some sort of toggle for other parts of the page. But e926 is literally just e621 with a forced rating:s search on top of it, so this is very unlikely to be possible.