Here are several cases where a user is not allowed to upload, though there is no permission error or something:

If a user (no matter if he's anonymous or registered without permission) is viewing a random unexisting file, he sees "No file by this name exists, you can [upload it]."
Please use a specific system message if the user is not allowed to upload.

If an anonymous user clicks on that link, he sees a specific message that you can customise. But if a registered user is restricted to upload, he will see only the message "This action is restricted to users in the group $1". I tried to use {{#ifeq:{{PAGENAME}}|Upload|information|normal text}} and I tried editing "upload-summary" but that only works when you are allowed to upload. Please make a specific message for this. This is really needed, recently a user on [[incubator:]] was confused of this and asked me how to upload, because it just says it is restricted to bureaucrats.

If a user inserts an unexisting image on a page, he sees a redlink (which goes to the error page I explained above). It would be better if this link also used "&redlink=1" so it won't go to the upload form when you're not allowed.

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Severity: normal