It seems that this is only possible if you add a user to the blocked list in github.
For issues with the the code you should use https://github.com/callmeal/Flickr4Java/issues.
However, to reach out to the author/maintainer with something not code related or bug, you should find out if he has his email or equivalent public.
For this particular library for example, you can reach out to the author through https://twitter.com/boncey, which ...
GitHub uses Markdown (specifically a custom 'flavour' thereof), and in Markdown you can escape backticks in code by using double backticks: https://github.com/mattcone/markdown-guide/blob/master/_basic-syntax/code.md#escaping-backticks
If the word or phrase you want to denote as code includes one or more backticks, you can escape it by enclosing the word ...