GDPR adds an interesting wrinkle in all this. GDPR requires both the right of removal (removing @-mentions) and the right of rectification (updating them.) So i

GDPR adds an interesting wrinkle in all this. GDPR requires both the right of removal (removing @-mentions) and the right of rectification (updating them.) So if I change my name from notJim to notJohn, GDPR requires* services to update previous @-mentions from notJim to notJohn, and similarly requires services to remove old mentions of notJim if I request removal. Using an identifier behind the scenes greatly simplifies this, because instead of dealing with text, you fetch the appropriate display name at render time. * IANAL, etc, and I'm sure requirements and interpretations of GDPR vary, but I do know that my company invested quite a lot into systems to fix this @-mentioning issue, so at least some people thinks it requires this and are willing to spend probably millions of dollars of engineering time to comply with said requirement. Personally, I support this provision.