No. What's the worst that happens? You take longer to do the challenges? The leaderboard is irrelevant, as you can only get on it if you're in the right time z

No. What's the worst that happens? You take longer to do the challenges? The leaderboard is irrelevant, as you can only get on it if you're in the right time zone/nocturnal/unemployed and really really fast, so what you then get out of it is a solid set of Haskell problem-solving skills. People learn languages in AoC every year. Do it! Some people do each day in a different language. Maybe don't do that...