When crafting this question about "404-page", I've tried give an example of not-found-page by using big question ID, for example this bare URL
https://serverfault.com/questions/5321111111. When I submit the question, the submit button reported an error with message "An error occurred submitting the question." Instead telling me about what's wrong with my question, the page tells me nothing.
Looking through HTTP status code, I see "302 Found" status-code followed by "500 Internal Server Error" like below.
This error wasn't shown when I put bare URL pointing to existed question https://serverfault.com/questions/5321
The error wasn't shown when I put bare URL pointing to removed question (but has question ID below 5321111111) https://serverfault.com/questions/532342 ,
This error also wasn't shown when I wrap the put the URL into non-bare URL like this.
Looks like Markdown parser for bare-URL was misbehaving in this case.
Why did meta.SE dislike my bare URL?