Capital dotted İ and dotless I errors
I'm learning with iPad app, which doesn't have an option to switch to a discussion directly from the exercise, so I cannot give the exact samples of the errors.
The problems is with the capital İ in İstanbul, or when iyi or iki occur at the beginning of a sentence and thus must be capitalized, and I typed so. But Duo doesn't accept capital İ there, and accepts only dotless I, while showing 'correct answer' with the dotted İ ! Even won't recognize it as a typo.
It is really annoying, especially with the 'health' meter - I had lost a dozen of 'hearts' until guessed how to make it.
It's a super frustrating problem. It will accept (at least for me) a lower-case dotted i, but will let me know that it should be "İ", like you said.
Likewise, for pretty much all of Duolingo that I've ever seen, punctuation never matters, I never use it, and never get dinged as wrong for it (though sometimes it will give me what I typed, but with punctuation, as an "alternative solution", or what have you...but there are a few sentences in the Turkish course, I believe one of them is:
Ona "seni seviyorum." dedim.
It was the last sentence I had one time and my health meter went all the way back to 0 from not getting it right, even though I knew I had every letter, letter for letter, like the answer had. I thought it was some glitch...until finally I realized that not only did I have to have punctuation in this one (which I did), but that it had to be exactly right. My phone defaults to the "smart quotes" that are actually curved one way or another, and Duo would only accept the straight up and down ones. it is highly frustrating.
> Ona "seni seviyorum." dedim.
Yes, it's exactly the phrase I had problems, too. My iPad doesn't make 'smart quotes', so at least here I didn't have problems, and I had guessed that it had to be quotes perhaps on the 3rd try... Instead iPad app capitalizes letters at the start of an input automatically, so the easiest way is to get used to type Istanbul with dotless capital I