This questin has been answered many time here, kindly search.

Links in comments are automatically converted to anchor tag, you do not need to filter them.

I have pushed demo file for fonts to git repo, Fonts folder. You can easily override any icons, simply use this filter: https://gist.github.com/rahularyan/5129d55940504155a2b4

Yep last one, I am using action.

I think its already on roadmap.

No, it does not exist yet for tags and category may be added in future.

Will be added in next update.

May be he is adding big image ? Image crop for cover and avatar will be added in upcoming 2.4.