I also thought it was optional / not required when using the male form. At least I understood the table in "tips and notes" like that. What do you mean with bug: is it wrong to use the "I" at the end? is it required or optional?
It is a direct translation of a full stop (.) And no, while writing you are supposed to use it after every sentence, so not optional but here on duolingo it should be optional since most of us here are beginners
Marked wrong for saying "हम पानी पीती हैं।" Why is that wrong? I'm rusty (going back to Hindi as a review), but I thought if a group was all female they'd use the feminine plural on the verb stem, right?
मैं हूँ / आप हैं / तुम हो / तू है / हम हैं / यह है / वह है / ये हैं / वे हैं are the conjugations in Hindi. हो (ho) is only used after तुम (tum) which is singular, "you." And हैं (hain) is used for plurals.