In the HTTP 1.1 Standard, it says that "If no Accept-Encoding field is in the request, any content-coding is considered acceptable by the user agent."
Which means that a server can, for example, return a gzip-encoded response body if the accept-encoding field is omitted.
In practice however, it seems like most commonly used servers (e.g. Apache, nginx) will not do this, and will send an uncompressed response if the field is omitted.
Is it fair to say that the more colloquial behavior is to only use encodings which are explicitly suggested by the client? This seems like a more logical course of action -- having the client give a list of encodings it can handle -- despite being contrary to the standard.