Chapters two and three are the lesson to not use procedural language fundamentals if you want performance, and to instead use functional equivalents. Not exactly a language quirk.
If somebody has only ever used 2000s-era Java and C# and those types of languages, functional style programming will be a strange beast. But python has enough functional style things such as lost comprehensions, and I hear Java and C++ have gained functional style programming too, so in this day and age I’m not sure that functional style programming should be considered quirky.
The runtime performance is all due to the current implementation, not the language itself. I think JavaScript has far more quirks, it then it was also invented in an insanely short amount of time so that’s not too surprising.
That's from 2010, even before JIT compilation in R became a thing. And since then, much has been done in terms of the computational performance of R.
Also, the author of R language said the performance of R is sub-optimal. In his own words: https://www.stat.auckland.ac.nz/~ihaka/downloads/JSM-2010.pd...
Currently I am using PyCharm with R plugin that JetBrains released very recently. R Studio is very slow and buggy.