I’ve had this happen twice now, though the first time I didn’t know what was going on, the second time it happened the change was much more visible.
So, while I am in the middle of writing a reply to Post A, the post is replaced with a different post in the same community. However, the comments remain the comments for Post A, despite the section at the top having been replaced by Post B.
Yes, this means on one page I have the post itself for Post B, and the comments section/replies for Post A
It is very confusing and distracting when this happens.
Two words: “race condition.”
One of my favorite server-crashing bugs was from the mid-'90s, before the web existed. Worked on a project to build, well, a mini-Web (though we didn’t really know that), a browser-like tool that ran on X-windows. It would let you search through an online library catalog. Everyone on the project sat down together to stress test the search engine. My student employee ran a search that began with a question mark, and it took out the search engine server.