Digital (video) artefacts are definitely a thing. Unlike with the CD, where we got to a point where over an hour of essentially perfect quality stereo music fits on this cheap mass-produced object, digital cinema is in a place where they can do something that's very good - much better certainly than what you'd see in a second rate cinema after a picture has been out for a few months and the print has seen better days, but it's absolutely not perfect and I can well believe it's not going to impress anybody who can see a nice new 70mm print.

Basically every frame of a digital movie is a huge JPEG. That's not quite exactly what's happening, but it's close enough. So you don't have inter-frame compression artefacts, as you'd see on a DVD or Youtube video, but artefacts in the individual still images absolutely are present, albeit rarer because they're using a lot of bytes for each frame. And so yes, text would be especially likely to make this noticeable as it is in JPEG on web pages.