C# isn't exactly quiet about this property, and yes, it can be annoying from an API perspective, but in C# this was likely a pragmatic choice to remain compatib

C# isn't exactly quiet about this property, and yes, it can be annoying from an API perspective, but in C# this was likely a pragmatic choice to remain compatible (and familiar) with C++, COM, etc. where most developers would be coming from. API members that operate on code points universally take a string and an index. That being said, treating strings as arrays of characters is fraught with peril in most cases anyway. You can't trivially reverse strings in any encoding, as you need to reverse the sequence of grapheme clusters (to account for diacritics, etc.). You can't trivially truncate strings either, for pretty much the same reason. You can't trivially grab a single character from the middle of a string, again, for the same reason. So basically, indexing, reversing, truncating, copying a subsequence, etc. are all not trivially possible regardless of the encoding. UTF-16 is not the main problem here, as even in UTF-32 it'd be broken.