(Not humans though, the Pinis were particular there were no half-humans for 'reasons.')
What I remember is that they followed the logic of (and I am STRONGLY paraphrasing here) "If you make an exception to the rule (i.e., Human-Elf hybrids being possible), that exception invariably becomes ubiquitous." That said, there was a one-shot/"What if?" story that featured a Half-Elf.
Originally Posted by dwig
In Tolkien elves and humans were biologically the same (no pointed ears on elves!). The difference was entirely spiritual.
A spirituality that enables Wuxia-flavored acrobatics, lightness of tread, eyes of the hawk, immortality, et cetera. Maybe I need to get religion!