The "translate" command started as something nice to have, probably on a whim by Marc (i.e. not an official feature), and was removed after being abused by many users.
Marc tried to fight it, e.g. in The automated Stack Exchange / Feeds user is now participating in chat but eventually gave up four days later and nuked this featue with a blast of "This is why we can't have nice things" all over chat:
Yes, yes; I was turning off the much-abused translate bot; I intended for subsequent use of translate: foo to result in that message, but... an if block got in the wrong place. Bad things. Very bad things. Fixed; data cleansed (but still tidying up a bit...)
I am pretty sure this abuse also prevented any further features, and we won't ever see anything like that again, as people will always abuse it.