As a Roblox developer, it is currently impossible to know what status code a server responds with when using HttpService.
Discord recently banned the use of the Roblox\WinInet user-agent string due to the fact that 88% of requests using that header did not abide by the Discord rate limits.
https://twitter.com/lolpython/status/967211473586987009
https://twitter.com/lolpython/status/967212535274340352
Due to the fact that HttpService does not support reading status code, Roblox scripts could not obey these rate limits in the official way.
(You could make predefined rate limits in the client side of things but this is not how Discord is intended to be used.)
This problem isn’t just exclusive to using Discord too, plenty of other web services communicate information about responses through the use of status codes.