>A browser is a 'User agent', as in it is supposed to act on MY behalf

It's supposed to implement the spec. Why are you and many other people on this site so attached over the wording of "user agent"? It is supposed to mean the software making the request, it doesn't mean anything more than that.

The argument is that the W3C shouldn't have included this feature in the spec, because it (allegedly) prioritizes the interests of publishers who want copy protection over those of end users who want to copy stuff. If true, this would violate the "priority of constituencies" HTML design principle: https://www.w3.org/TR/html-design-principles/#priority-of-co...

As it happens, the relevant standard actually includes a response to this argument (https://www.w3.org/TR/css-ui-4/#valdef-user-select-none):

"As user-select is a UI convenience mechanism, not a copy protection mechanism, the UA may provide an alternative way for the user to explicitly select the text even when user-select is none.

Note: none is not a copy protection mechanism, and using it as such is ineffective: User Agents are allowed to provide ways to bypass it, it will have no effect on legacy User Agents that do not support it, and the user can disable it through the user style sheet or equivalent mechanisms on UAs that do anyway. Instead, none is meant to make it easier for the user to select the content they want, by letting the author disable selection on UI elements that are not useful to select. Tools such as CSS validators, linters or in-browser developer tools are encouraged to use heuristics to detect and warn against incorrect or abusive usage that would hamper usability or violate common user expectations."