Looking at Conduit API calls I've found these:

• differential.createcomment - for creating comment
• differential.createinline - for creating inline comment

I believe, that similar calls should exist for Diffusion as well.

Also if possible please expose a flag (through API) that allow to make inline comments as linter errors. I want to use this to extend Phabricator in what that allow to inject Code Style violations (that are only discovered when commit-triggered build on Jenkins side finishes) into commit on Phabricator side.

If you please could explain how these new API calls can be created and what fields should they allow as input, then I'm willing to do all the coding.

P.S.
I'm not sure if Conduit allows to group API calls (e.g. when I want to add 100 inline comments, then I surely don't want to make 100 network requests for that), but at least for inline comments this can be a good idea to allow adding several ones per single API call.