@kctipton well much like the far-right it is hard to distinguish which statements originate from the russians/china themselves. The only clue we have is the friendliness of the far-right/left, and the general consistency in talking points, often expressed in ways that are self-defeating or meant to be divisive.
depends on the country you are talking about. In the USA a huge portion of the left is "far-left" and radicalized in all sorts of ways (just as the USA has a huge far-right problem)... Thankfully in much (not all) of the rest of the world you'd be right, there isnt much of a far-left or far-right in say, the Netherlands. The prevelance of the far-left seems limited to the USA, but for anyone not on the extremes of the spectrum they are a very obvious and pervasive group for sure.
In fact the USA is so polarized they tend to exist on the extremes of almost any issue, even non-political ones.