Question

If the variable is local to the current scope, is there any reason to set them to null right before the end of it?

{
    var com = new AComponentObjectModelInterface();

    // something goes here
    // ...

    com = null; // why?
}

Answer 1

Maybe the developer that used this was migrating VB6 code manually. But he ignored that

Set aComponentObjectModelInstance = new AComponentObjectModelInterface

// something goes here
// ...

Set aComponentObjectModelInstance = Nothing

should be translated to

var aComponentObjectModelInstance = new AComponentObjectModelInterface();
try 
{
    // something goes here
    // ...
}
finally
{
    Marshal.ReleaseComObject(aComponentObjectModelInstance);
}

instead