While I was writing an answer to this question, my browser tab crashed. That's a browser bug, obviously, not a Stack Exchange bug, but it's also partly two Stack Exchange bugs:
- The preview code is obviously being too demanding on the browser.
- Stack Exchange saved a draft of the answer, but that draft was missing about 90% of what I'd written, which is pretty useless.
My browser is Chrome 85.0.4183.121 on Linux/x86_64. I blame the crash on the preview code because I noticed that as I was typing, the preview updates took longer and longer (maybe about ½ second just before the crash). Previews have been consistently taking longer than they used to (it's a noticeable amount of CPU time, even without MathJax or code formatting) for the past few months; I'm pretty sure this started with the switch to CommonMark, because I noticed it happening without a browser upgrade (or even restart) and as far as I recall now this is the Stack Exchange change that had just happened. My answer was moderately MathJax-heavy, with about 20 simple MathJax fragments: I've written answers that were a lot heavier in the past, but none since the markdown engine switch.
Eventually, at one point, a preview update locked the tab up for several seconds of CPU activity, then the tab crashed with an “Aw, Snap!” message indicating a SIGTRAP. I didn't have time to check the memory usage before the tab crashed, but it can't have been that bad, because my system (which has swap) wasn't thrashing.
Unfortunately, I don't have a copy of what I had typed. I may or may not post something vaguely like it later if I have the courage to write it again.