I agree. The OP blog post is mistaking. I think the real language misuse is on the behalf of Person A. When asking whether you "can do something in the Foo programming language" this could be a question of theoretical universality or a question of practicality. If it's one of practicality, then it has nothing to do with Turing universality. If it's theoretical, as in "is Foo expressive enough to describe such and such a computation at all", then universality matters.

Also, from a computationalist's perspective in Philosophy, Turing completeness literally does mean being able to do anything that a single-taped Turing machine can do (such as writing a GUI or writing to a screen). If you a priori disconnect your Turing machine from the screen, effectively eliminating the logical possibility to print to it (or, similarly, you use some pared down language where specific functionality is intentionally left out) then it makes no sense at all to bring Turing completeness into it. It seems like the OP either rejects the Extended Church Turing thesis, or mistakenly thinks that other people lump all possible hardware limitations into Turing completeness. If a language is resource bounded, then it is only Turing complete w.r.t. a Turing machine that has the same resource bounds.