A new method, to see which one is interesting, could be to display the
reputation of the person who upvoted
But surely the title, tags, topic, and question itself is what makes a question interesting?
A user's rep doesn't really have any bearing on whether they are interesting, vote on interesting questions, or have even voted in the same way for the same reasons you do.
and has the largest reputation among upvoters
Wouldn't this alienate low rep users in some way?
Is a person not interesting because they have a low rep on a certain Stack site?
Also, wouldn't we need to consider their rep on other similar sites?
For example, if a user has 150 rep on Programmers site, doesn't it have some bearing they have 50,000 on both Stack Overflow and Code Review?
Then new questions could be filtered using this upon demand
Rep does not equate to anything useful. A user with many poor questions/answers, and has nothing particularly interesting or useful to add to posts, might have a lot of rep they've accumulated over time over many posts.
And a low rep user (say 300) could be a developer for NASA/Google/etc and just joined the site.
And this won't always be users with 300K rep which might interest you, as often average or even low rep users will be the highest rep user who voted.
For the most part, you'd just see result like 1,523, 8,295, 457, 289, 18,443, etc.
Why is that useful, interesting, worth sorting result by, or good for anything really?
And users with higher rep are more likely to vote on interesting and decent questions and answers, which means you can already find them from higher voted questions/answers and the more interesting titles and questions.
(Note, I said more likely, not "always").
or everyone could see the ones already upvoted by someone whose
reputation is at least 10% of his own reputation.
I really do not know what benefit you expect from this "restriction".
Take my SO rep, 1.8K.
Why do I only want to see rep from users who upvoted who have 180 rep or above?
And is my vote not interesting or is it meaningless to all users above 18K rep?
What about users with say 30K rep. Why do they only want to see rep from users upvoting who have 3K rep or above?
I just don't see any reason why a user's rep would ever be of any interest within the scope of voting.
Knowing who voted would be interesting, but that will never happen (and I agree it shouldn't).