I think my comments are justifiable even in light of keeping special-case comments minimal and non-confusing:
a) Creating a separate, truly integer-based map function, say categorize(), would alleviate the need for complex documentation. Otherwise, suppression of documentation for discrete math would be suspicious.
b) Minimizing documentation would surely call for removal of the misleading 10-to-8 bit example--it is needlessly incorrect for discrete math.
c) If we are concerned about minimizing special "facts", then the comment regarding using values out of range may be a candidate for removal. It has a pitfall in that the pattern changes near in_min, so why promote it without caution? On the other hand, a proper introduction to the purpose of this function can clarify a great deal of misconceptions.
d) It's inescapable that the switchCase example sketch needs to be corrected. It's wrong in the same way as jj33 introduced in this thread.