"The man is resting."
This is a very minor complaint/issue, but the first time I saw this sentence, I gave the English translation "The man is resting up," since the -lI' suffix suggests that he is resting towards a specific goal. I thought this was actually a better translation than simply "the man is resting," since that sentence doesn't necessarily suggest that there is a goal to be achieved in the resting, and the suffix -taH is better suited to that. But my translation including the final word "up" it was rejected as incorrect. I don't think I reported it as an alternate translation, as I thought I would like to get some feedback first.
I should probably add that while the top of this page indeed says "leStaH loD," I have got this sentence using word tiles (English to Klingon) this time, and leStaH isn't one of the available options - only leSlI'. I'll save a screenshot of the screen as evidence, but I'm afraid I have nowhere to post it at present.
"Resting up," sounds good to me. I've added it as an accepted translation. leSlI' is actually the primary translation, but leStaH is also given as a "best" translation. It is particularly odd that it would show you -lI', which is the primary translation, but then title this discussion with -taH which is the secondary translation. Duolingo does some funny things sometimes. No need for a screenshot.