I understand.

I reported this issue when one of my newest tests failed with Python 3.10 and 3.11. Actually, using friendly-traceback, using the location of the exception as indicated by cPython 3.10 and 3.11, here's part of the explanation it gives:

    The following lines of code would not cause any `SyntaxError`:

        sum + [i for i in [1, 2, 3] if i%2==0]
        sum - [i for i in [1, 2, 3] if i%2==0]
        sum * [i for i in [1, 2, 3] if i%2==0]
        sum, [i for i in [1, 2, 3] if i%2==0]
    Note: these are just some of the possible choices and that
    some of them might raise other types of exceptions.

So, I agree with you that suggesting a comma would be appropriate.  (I also miss the suggestion of inserting an equal sign above).

Meanwhile, with prior versions of cPython, here's the suggestion that was offered:

    You used square brackets, `[...]` instead of parentheses.
    Write the following instead:

        sum(i for i in [1, 2, 3] if i%2==0)

So, since using the suggestion currently by cPython (3.10, 3.11), one could get a syntactically valid statement by adding a comma, I cannot really argue that this is a bug. (Sorry, I should have checked in more details before.)

Therefore, I agree that this issue should probably be closed ... unless you find that suggesting a missing comma while there are many other possible operators that could be inserted could be considered as misleading.