Someone decided that we need competing tagging scheme for tagging access and created access=restricted. See https://wiki.openstreetmap.org/wiki/Tag:access%3Drestricted and https://wiki.openstreetmap.org/wiki/Talk:Key:access#Maybe_introduce_a_Key:access.3Drestricted_.3F
JOSM already complains about it and it would be useful to do the same in iD ( note that it is used 6k times, not so often to consider it as a real competitor of standard access tagging but worth adding validator warning to stop it - see https://taginfo.openstreetmap.org/tags/access=restricted )
So... Someone introduces a tag 5 days ago.. it's now used 6k times.. and you want us to write a validator to stop people from using it?
come on...
Tag is certainly much older - random example from 5 years ago ( https://www.openstreetmap.org/way/266904074/history )
http://taghistory.raifer.tech/ shows that most of uses was added by import/automatic edit and that usage is slowly decreasing since 2015

Tag is certainly much older - random example from 5 years ago ( https://www.openstreetmap.org/way/266904074/history )
Oh ok.. Sorry, it sounded like you wanted to use our validator as ammunition in some wiki edit fight you are currently having with some user.
I don't see anywhere a consensus that the tag is deprecated, and I would expect to see more discussion of this for a tag that's been around for 5 years. I just see that you created a wiki page today (and are continuing to edit it) and are talking to the other person on a forum and on wiki comments this week and maybe the tagging mailing list.
I'm ok with having iD just suggest "upgrading" the tag to access=private. As long as there is actual consensus and nobody is using the tag for anything.
JOSM complains about it "access=restricted is unspecific. Please replace 'restricted' by a specific value. (1)"
And from what I see it is not considered as controversial.
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Oh ok.. Sorry, it sounded like you wanted to use our validator as ammunition in some wiki edit fight you are currently having with some user.
I don't see anywhere a consensus that the tag is deprecated, and I would expect to see more discussion of this for a tag that's been around for 5 years. I just see that you created a wiki page today (and are continuing to edit it) and are talking to the other person on a forum and on wiki comments this week and maybe the tagging mailing list.
I'm ok with having iD just suggest "upgrading" the tag to
access=private. As long as there is actual consensus and nobody is using the tag for anything.