Maybe sort entries in the "sentences" tab under discussion by activity?
As far as I see the sentences are sorted in reverse order of when the first post was made for that sentence.
This leads to new sentences being on top of the list when you click on "sentences" and older sentences don't appear at all.
Maybe it would help with getting answers in the sentences discussion, if users could see what discussions are active.
Oops, I guess I didn't understand your post the first time. I'm sure the logic of the ordering is that there can easily be 10,000+ sentence discussions in a course. Most of them have comments; a good number have many, many comments. Hopefully, there's someone in them able to give actually authoritative responses (although there may well not be) still active, or at least active enough to answer new, unaddressed questions that people ask later. The course moderators have a way to see all new questions posted (the Spanish course could probably use a few more active mods to split the work given the huge volume...). For other users who may be able to answer but aren't mods, there's the Sentences tab. Arguably the highest-priority threads for them to address are the newest ones, the ones that no qualified answerer has had a chance to ever address yet. Hopefully, those that answer a first question will go on being so willing.