The truth is that it is something that I have always wondered, for many years in Linux we have setfattr / getfattr and setfacl / getfacl, however this has never been brought to a graphical environment and I do not understand why because it is something extremely useful.
Other operating systems like MacOS perfectly support file tagging, we in Linux have the setfattr / getfattr tools but they are of little or no use in GNOME because the system ignores them. Wouldn’t it be interesting that Nautilus together with Tracker use this functionality? Don’t you think that being able to tag files adds would be something desirable?
On the other hand, there are access control lists, another thing that GNOME completely ignores (when displaying file information). From Nautilus you can only see or modify the most basic permissions (user, group and rest), but there is a whole world of possibilities with the ACLs that the user loses by not having an interface for it. For example, Windows solves this problem perfectly. Couldn’t something similar be done in GNOME / Nautilus? Don’t you think it’s a good idea?
I think on GNOME for file tagging instead GIO file attributes would be used. That can be (and is) used to store file metadata. For ACL support there is the Eiciel plugin.
For both suggestions might you add examples of what users would use these features? For more fruitful discussion. What does file tagging add that is not already covered by file starring for most users? Why would users care about ACLs? What would they use ACLs for outside a server?
For me both functionalities do not have the same weight. I think it is more interesting to initially have the first one (file tagging) than the second one (access control lists).
In the first case, I believe that marking a file as a favorite (star) is complementary to being able to tag files. It is necessary to bear in mind that the labels are arbitrary (the user can use the ones he/she wants) so there are many applications for it. For example, in a collection of movies you could mark those that are romantic or action movies and then search by that tag to list only those you are interested in. Or in a collection of photographs, you could tag with the name of your pet those in which it appears and then find them quickly. There really are a lot of uses for this feature.
In the second case, the ACLs, it is true that perhaps they are designed more for a server than for a workstation, but it is a question of giving that flexibility and (above all) ease of use to the users. Personally I manage the ACLs from console, but we must think in users that do not manage well out of graphical environments.
It is also possible that in a family the same PC is shared between different users and ACLs would be applicable in that case. Yes, it is clear that you can simply create a group to avoid the use of ACLs, but sometimes (especially for people who come from using Windows) this way of working is not intuitive because for these people the most logical thing to do is to access the properties of a folder and say that two or more users can write in it.
All in all, I think both features are very interesting and I would really like to see them as part of GNOME someday.
I would also love to see tags as first class citizens, and have volunteered some time experimenting with this in the past. (e.g. here).
In the end, when I want to categorise files I usually find some solution that doesn’t require tags. For example, you can create folders for your movies representing “romantic”, “action”, etc. and then symlink the actual movie files into the folders. Nautilus can do this today. Also, various media player apps / content server apps already support tags without depending on specific features in GNOME.