Load this userscript in Tampermonkey, Greasemonkey, Violentmonkey, or any extension of this kind.
Click the file named userscript.user.js (not the other one without the .user. in the name).
Once opened, click the Raw button.
At this point your extension will take control, and will ask you if you want to install it.
It adds 2 links (named "(r)") to sort by "recently updated" (issues & PR tabs)
And in the GitHub page header
On the page displaying all your Pull requests, or Issues, a new category ("Commenter") now appears.
Clicking this button will display all the issues/pr in which you made a comment. They might not appear in the other categories.
