Jeremy Stangroom

It's very uncommon in Linguistics. Maybe some other disciplines have lower standards. It certainly looks as if the examiners didn't do a very good job in the case under discussion.

It can, depends in the methodology, epistemology and ontology used. Being a subject within the research is not a reason in of itself to have issues with a PhD unless the methodology explicitly demands it.

I just find it very odd that no corrections were required. I have examined the PhDs of students who went on to be professors and corrections were always required. Good examiners will always find imperfections if they look for them.

Passing without corrections needed does happen, but it's pretty rare.

What discipline or disciplines are you thinking of? I've never known a PhD in Linguistics passed without corrections.

I've known a sociology one from personal experience, but I can't say I have a huge data set to work from

One of my colleagues has just had a law PhD passed without corrections. When I passed mine all it needed was one sentence changing. It depends on the quality of your supervision and feedback. Just like how, sometimes, articles for journals are accepted as is.