Allow users to login and mark breaches they dealt with
My data was in the 500px breach. Every time I check for breaches against my email address on HIBP, this comes up. I use random passwords so I am not concerned about the leak, but I do make sure to change passwords once I am notified of a leak. Once the list of breaches becomes long enough, I may not remember whether I have dealt with a specific issue reported. It would be good to have a mode where I can log in and check the issues that I have dealt with, so the next time I login and check I can see just the new breaches to deal with.
It is possible for the user to handle that entirely on their end by checking the last time the pwd was changed in the password manager, but it can be tedious when the list is long...

HIBP is not intended to be a personal triage tool, it’s a reflection of breaches at a point in time.
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Marco Lestuzzi commented
Once the email reporting the violation of your password is received, it would be interesting to be able to click on a link likes: "done, the password has been changed!" and ensure that if the same email is searched for, it appears that it is no longer problematic. This operation, of course, only applies if initiated by clicking the link within the email related to the same email being searched.