Giving a lingot as a thank you
There's been a few times where someone helped me in the exercises, or posted something great in the forums.. and a "thx" just don't seem enough.
I'd like to give/donate/tip the person with a lingot in cases like those :)
The problem that I have with flaunting lingots is that people can easily gain a lot of them by redoing easy things over and over. It's not like, say, the language tree trophies that you have to actually work hard at getting. So I see it as a useless sign of prestige.
I agree that lingots should be a lot more useful though. I hope we get Duo avatars eventually that we can spend lingots customizing.