User A PMs User B
User B receives an email notification. Wants to respond, clicks “Visit Message to response to…”
Browser opens, User B has no cookie, and sees a 404 “Ooops! That page doesn’t exist or is private”.
There is no login button, nor any suggestion that there is any way to make things work.
At the very least there should be a suggestion that the user might need to login to make it work?
But - much better - it should automatically start the login process (which might well automatically succeed in SSO deployments)