Requested feature overview description.
Basically an option in the user settings or blacklist panel that makes it possible to show thumbnail, albeit blurred, of blacklisted posts, and at the same time show the proper post when it is being viewed. It is possible to achieve so with a StyleBot or any CSS addon by using something akin to the following:

img[alt*="gore "] {
  filter:blur(5px);
}

However a proper in-site feature would be more viable.

Why would it be useful?
Some "global" tags you might feel comfortable or not depending on where you see it. Example: with "gore", there are some that are minimal, passable, wouldn't bother the user, there are also some that may be too much, and at the same time they do not want to see a full page of it uncensored, and blacklisting "gore" as a whole might hide some that doesn't bother them, whether it's from an artist they like or from an artist they are unfamiliar but might interest them.

What part(s) of the site page(s) are affected?
Presumably Posts and Pools

Alternative to the example in the OP that reveals the thumbnail completely when hovered:

img[alt*="gore "]:not(:hover) {
  filter:blur(5px);
  transition-duration: 0.5s;
}

img[alt*="gore "]:hover {
  filter:unset;
  transition-duration: 0.5s;
}

I found this to be a better approach, as it includes a transition effect to/from blur

https://e621.net/users/155625/edit -> Advanced -> Custom CSS style
No addon needed?

alphamule said:
https://e621.net/users/155625/edit -> Advanced -> Custom CSS style
No addon needed?

Wow, that is VERY off the road.

Plus that alternative requires too much trial and error, while the addon approach I'm using has results on the fly.

But yeah, ideally a feature that does without having to deal with Custom CSS is what I am proposing.

alphamule said:
https://e621.net/users/155625/edit -> Advanced -> Custom CSS style
No addon needed?

I've never had any luck trying to mess with the .blacklisted class's CSS in the stylesheet. presumably it's because there's some JS stuff going on after the page loads that causes it to not work.

sipothac said:
I've never had any luck trying to mess with the .blacklisted class's CSS in the stylesheet. presumably it's because there's some JS stuff going on after the page loads that causes it to not work.

It's because blacklisted posts are set to not load in their thumbnail in order to save memory and bandwidth. CSS can't do the necessary things in order to load the thumbnail, either, so any CSS wouldn't really help, as far as I can tell.