I don't know that I've ever seen anything strictly _wrong_ in an article about mathematics, but I've certainly seen articles giving equations without defining what any of the variables are and using using very field-specific notation without defining or referencing it, making them impossible to read unless you know enough about the topic to reverse-engineer what they're talking about.
And I'm not talking something like using a Dirac delta without referencing it; I'm talking about pretty esoteric notation that is really only relevant to the topic of the article.
And of course plenty of the math articles are just not very coherently written (and yes, plenty are quite good).
I'll go ahead and admit that I'm a dummy: I find anything related to math on Wikipedia to be an incomprehensible nightmare. There's a consistent failure, in my view, to consider the audience. It's like people are writing to impress a technical in-group rather than to inform the general public.
Maybe I should try the Simple English pages instead. :-/
I think you're spot on, for what it's worth. The context for my comment above is that I have a math PhD, and even then a lot of the articles are an unnecessarily tough read. For the general public they are pretty impenetrable...
Can you point to a few examples just to make sure we are talking about the same thing? I use wikipedia for math, physics and engineering topics frequently and generally do not have too much trouble understanding it, possibly with a few cross-referenced articles.
I have seen occasional weird writing, but this is usually either some esoteric subject or just an initial writeup on a narrow topic -- that is, an inexperienced author trying to fill a void, not someone staking out territory or looking for recognition. Just my experience.
If I had examples off the top of my head, I would have cited them. I'll see if I can find time to do some digging through my browser history, but this is a multi-hour endeavor that you're asking for here, so I might not be able to get to it.
And to be clear, I am not talking about people staking out territory or looking for recognition. I am talking about articles being so badly written they are functionally indistinguishable from being "wrong". Yes, you can decipher them with enough outside knowledge and some other references, but it's pretty tough. And this is not a majority of mathematics articles by any means. But the problem is that if you don't know enough you can't tell whether you're looking at such an article or not, unfortunately...
P.S. I just took a quick look at just my recent-ish Wikipedia edits, and https://en.wikipedia.org/w/index.php?title=Limit_superior_an... was correcting a small but obviously wrong claim. Which is, to be clear, not the sort of issue I was referring to in my comment about badly-written articles.
And I'm not talking something like using a Dirac delta without referencing it; I'm talking about pretty esoteric notation that is really only relevant to the topic of the article.
And of course plenty of the math articles are just not very coherently written (and yes, plenty are quite good).