As for {Let's do it!}, that's certainly true. I always see it in Elemental DC, but it's rarely seen in Gaia. Elemental is located in Japan, but there are many English speakers. So auto-translation is commonly used there.

Auto-translation is often used not for translation, but simply to save typing effort. On the JP DC, you will sometimes see {Doma Castle} or {Domakin} used in response to an apology. They don't make sense in other languages. In Japanese, "Don't mind" is used with a nuance similar to "Never mind" or "Don't worry about it". This changed into "Doma". I think it is similar to how {Ok'Zundu} is sometimes used in place of OK.