Thanks! and sorry for undeserved attribution of a bug.
On screenshots you can see no errors in the Console and no stars-buttons in the Composer or the
The plugin works well if the post is created in the rating-enabled category initially. However it doesn’t work for the posts in such directory which have been created/edited before error-less installation of this plugin (i.e. I had some Discourse-related error on the server when initially installed this plugin, but after rebuild there was no error).
Unfortunately the plugin doesn’t appear to be working for the posts initially created in a non-rating category, when those posts have been moved to a rating-enabled category, which is sad :’(