When I type this
I get this
How can I get the fraction properly centred?
Edit: testing another version here (typed, not pasted)
displays correctly in Chrome and in the Android app
Pasted from 3 versions that display wrongly in the sandbox: $$\left|\frac xy\right|$$
Further edit: I think it might be the browser getting overloaded. I noticed after inserting the above versions that they the two that did display were momentarily misaligned as in the screenshot, then corrected themselves.
Update: I left the misdisplayed version open in Chrome while I went away to do something else. When I came back 15 minutes later, it was displaying properly. That doesn't prove that it's the browser struggling, but I'm happy to assume that it is. So problem solved.