If someone says "I use this profile for my working space" it is so general that it means almost nothing.
How so? You now know the numbers and their associated scale. That be true if it were a working space or not. Numbers without a scale are menainless. So the sentence you propose provides some information. Why the conversation comes up is questionable but the statement is complete.
It could be the space of the color profile selected in the Color Settings, or the embedded or soft proofing color profile of the image.
Yes it could. So what? If I tell you my working space preferences in Photoshop are set such that ProPhoto RGB is loaded as my preferred working space, that tells you one thing. It can be set as such and I can open a document in sRGB and tell you this. Again, each piece of information is complete. It doesn’t need to referece the other. You know what I prefer to use for my editing space (for new documents), what I expect Photoshop to assume for untagged documents (which I never encounter because they are bad news). In another sentence, I’ve told you the working space of the data I’m currently working on (sRGB) which is completely separate from the working space preferences I have set.
It could be also someone talking about profiles like monitor or printer profiles assigned as a working space in the color settings (I gave a couple of examples when this is practical and saves time) and such person has full right to say it that way - what else he can say - "I'm using non-working color space for a working color space"? It sounds funny isn't it?
Not at all. You seem to expect the term working space to carry over as an ambiguous tag and that’s not useful. If you tell me you have assigned your display profile to the 3D data because its untagged, I fully understand the numbers and their associated scale (color space). Photoshop does too and handles the data and color appearance correctly. If you tell me you opened a document from ACR in ProPhoto, that working space has nothing to do with the 3D image.
I know and agree that it is not well behaved, highly device dependent and has lots of idiosyncrasies, however I'm not sure about the zero reasons.
Give me more. Other than telling the color managed application the meaning of the numbers, why would you continue to use such a space? Its not well behavied. Its unqiue to your display based on the day you made that profile (which may be different in a few weeks). Its useless outside ICC aware applications. So inside an ICC aware app, what’s the resaon you’d stick with this color space?
The color spaces of most wide gamut monitors are quite different than Adobe RGB.
Yes they are just as the color space of sRGB gamut monitors can be quite different than sRGB. All I have to do is calibrate the display with targets that don’t match sRGB and guess what? Its not sRGB. Its questionable any modern LCD that isn’t using P22 phosphors produce sRGB as its defined. And they don’t have to! That’s WHY we divorce the working space from the display. If your data is in sRGB, its the same on any one’s machine. Your display profile describes one color space of one display on one day that may be different the next. Not so with sRGB or any of the synethic working spaces. That’s why we use them!