I think we should change the variable names to indicate ownership. This is only important for allocated data, generally passed by pointer. (floats, etc. get copied) Ownership in this case comes down to who has the right to deallocate the data, caller or callee.
Errors from misunderstanding this distinction
result in two bad kinds of errors. First, if both deallocate the data, the program will usually crash. Second, if neither eventually deallocates the data, then the program has a memory leak. Leaking memory can result in poor performance and eventually a crash due to lack of memory.
I don't have a concrete proposal for how we should change the names. For calling arguments, one way of passing the data "gives" the data to the called function. The other way of passing the data "lends" the data to the called function. There is also a similar division in return arguments. A returned value can be "given" to the caller, or it can be "lent" to the caller. The distinction in return values could possibly be indicated in the method name.
