REPORT. Don't complain
Report a sentence whenever you think your translation should be accepted. DON'T complain or mention it in the discussion sections, please. It is unnecessary and unhelpful in contributing to the BETA, which is expected to be riddled with unfinished alternative translations and mistakes.
I say this so that people hopefully keep things clean, and that whenever one sees that (3), it should be about grammatical structure or a fun fact about the word that was used, or maybe someone has a pun or a question about something that I too wondered about, instead of seeing it clogged with "My translation 'blahblah' was marked wrong!".
Use the report function.
Actually, if there is a problem with the audio on our end, the contributors can usually figure out what's wrong without an explanation, especially since there are usually freewrite reports from Android users too. Comments in the discussion may well not be seen at all.
I have to disagree with you. I bet there are tons of reports where the users report a wrong consonant or similar. The contributors can clearly address these reports.
But those users usually haven't read any articles or descriptions of Classical Latin phonology. Have the contributors read any? I just see no way how reporting would help. At best it would be overshadowed by hundreds of false reports and at worst it would seem like a false report to contributors.
Lastly, audio is always corrected very slowly on Duolingo, if at all. The users should be informed by the community then.
It's been quite some time since I've seen freewrite reports. These would be useful of course.