CSDL XML Section 12.9 Paramerter
First paragraph:
An action or function overload MAY specify parameters.
 
Problem: Even an action or function that isn't an overload may specify parameters.
Second paragraph:
A bound action or function overload MUST specify at least one parameter; the first parameter is the binding parameter. The order of parameters MUST NOT change unless the schema version changes.
 
Problem: Ambiguous as to whether parameter ordering may (or may not) change seems linked to whether we are referring to an overloaded, or non-overloaded, action or function.
Since I originally identified the issue about parameter ordering, I can assert that I wasn't concerned about ordering only for overloaded actions/functions. It is important for parameter ordering to remain stable for non-overloaded actions/functions. (Otherwise client applications using code generated from model elements will experience backwards-incompatible changes in method/function signatures).
Furthermore, the "Element edm:Action" and "Attribute Name" parts belong in section 12.1 "Action", not in 12.2 "Action Overloads".
Similarly, the "Element edm:Function" and "Attribute Name" parts belong in section 12.3 "Function", not in 12.4 "Function Overloads".
Proposal
Distinguish between
- an action/function as the named set of all its signature definitions aka overloads
 
- a single signature definition aka overload
 
Imported from ODATA-1370