Before we discuss which REST constraint we should follow and which ones we should not, let's underline one very important distinction: REST is an architectural style, and does not impose low-level implementation details.

REST is a generic set of rules/patterns that you can apply to any API. We commonly use it to structure HTTP APIs, because HTTP is the protocol of the World Wide Web; however, the HTTP protocol and its verbs are in no way tied to REST.

Having said that, Roy Fielding, the author of the REST specification, was also the chief architect of the HTTP/1.1 specification, and so the REST style fits very well with an HTTP implementation.