Is it possible to completely remove an issue from the GitHub issue tracker?
Users are unable to do this, including repository owner.
But issues can be deleted by Github support. One may contact them and request deletion. It may be delayed or refused but it is an available option that can be used.
You could by just asking to github to ban the user that created the issue
Public feature request
I wrote to GitHub in 2014-08 and https://github.com/jdennes replied by email:
Thanks for the suggestion. It's only possible to edit/clear the issue content currently. However I've added a +1 to this suggestion on our internal Feature Request List.
confirming it was not possible.
Best workaround so far
set the title to something that will never conflict with any search, e.g. a single dot .
.
This may not hide the history of your blunder entirely because of the automatic undeletable "changed the title to" comments.
make the body empty
GitHub staff has the power
If something is a security issue, contact GitHub staff, they usually reply quickly, and are able to remove issues for good as can be seen at: http://archive.is/OfjVt which has issue 1 and 3 but no 2.
As of 04/2019 not all issues can be deleted current work around is to edit the issue then delete the edit history, the only downside is that the issue still exist and the old title could be seen.
You can edit an existing issue (let's say if it's a duplicate) and you can change the title, description and target milestone to be something completely different. That's as close as you can get to removing the ticket, AFIK.
You can delete the entire repo if it's really important.