Smoothing Xp curves

[Shendare]

I was able to find this mention:

Hell Levels 50-60 - [ Link ] (September 4, 2002)

We have smoothed out level progression from 50-60. This should
mitigate the "penalty effect" that occurs in levels 51, 54 and 59. Note
that it will cost the same experience to level from 50 to 60 as it did
before. Also, death experience loss will appear different in some
levels. This is an unfortunate side effect that must remain to prevent
some experience exploits.