Please fix the bugs with "words" list, etc.
First, let me say that posting problems with the app here is effective. For example, I was stuck at 54% for almost 4 months and now my percentage is steadfastly increasing. Thanks Duolingo -- it may be kind of anal, but its comforting knowing my diligence is paying off.
Now I need you to fix the "words" learned so they reflect accurately what I have studied -- prevents redundancy in practice. More specifically, my list says that I have not studied "animals" in over a year and no matter how many times I complete the course "elefante" remains at the bottom of my list. Also, I don't understand why I don't receive my bonus lingots every 10 days or why I don't get the little prize icon that everyone else gets acknowledging that achievement. Like I said, I know I'm a little anal, but when you're on a 463 day streak like I am a little acknowledgment goes a long way lol.
Prize icons (badges?) are only included for people in different test groups. So, you're not the only one who isn't getting the badges.
The fluency percentage doesn't go all of the way to 100. For most courses, it maxes out between 50-70%. It's nice to watch the number go up and if they go down it is probably because the strenght of some of your words have decayed for lack of practice. It is also possible that Duolingo is experimenting with word strength decay rates and/or how much decay rate effects fluency. However, outside of being a fun number to watch go up and down, I wouldn't put much stock in the fluency percentage. It's not accurate in a real world sort of way.
As for bugs, they go on a to-do list and that list is ranked by priority. So, if there are always things that are higher in priority being added to the list, a low level bug won't get fixed any time soon.
PS Since you mentioned your streak, I recommend checking out the discussion: Checked your streak freeze today?. It could be beneficial. :)