"language_not_allowed" error when trying to submit a comment using Jerboa.

I was trying to reply to a Taco Tuesday post and no matter what I replied, I got a popup which said, "language_not_allowed".

Looks like placeholder text that was never filled in. What is that error trying to say?

I initially posted this:

Fish tacos are my favorite. Crunchy coleslaw, beer battered cod, a big ol' scoop of sambal oelek, and I'm in heaven.

I removed the "sambal olek" because it's a foreign language, but I got the same error. It persisted even when trying to post "just testing".

Any ideas?