Without Github, contributing to OSS would have been much harder for me (being a noncoder). Thank you for giving us a tool with tremendous leverage in many aspects, both technical and nontechnical.
While it's true that everything can be done in the browser, "saving = committing" there so I prefer to use the terminal and emacs.
In the best case, you can simply reproduce it. Then say so in a comment to the issue. However more probable, you have to ask the reporter for more details or try different versions and environments.