Just because its relatives MIGHT have had feathers, doesn't mean the last of the kind had. We don't have any feather impressions to confirm if he had plumage as well. Therefore, "some dinosaurs known to be feathered, like Tyrannosaurus" is not true. It's possible, but you can't really say it as a fact.
My point is that feathers are not like hair. Comparing dinosaurs to mammals in matters of integument is a great mistake, for dinosaurs lack the brown fat which isolates mammals. Feathers, however, act as an isolator both for warm and cold temperatures.
Sorry for the delay, Sergey. It's not a problem with my eyesight, I saw the plumage you drew. My problem with the depiction is that it's somewhat contrary to the paper itself. The described filaments are way longer and the plumage much more extensive than you showed here.