As you can see the console output seems to be set too narrow. I can try to fix this by manually setting e.g. options(width = 70), but that is quickly overrun by RStudio so the problem reoccurs.
I have had this problem with quite a few recent versions and am now on RStudio Server 1.4.1073.
I've noticed this issue as well, and as far as I can tell it occurs only when using certain fonts. My understanding is that the output here is generated with the expectation that the characters are of a certain width, and so will fill the horizontal space exactly.
I'm not exactly sure why this is the case, but to test, you could try switching to different fonts to see if they are affected in the same way. (It could also be helpful to know which fonts are affected and which are not, if this is indeed the issue)