I'm building my own, so it's possible that stuff isn't perfectly right just yet. I'm building stuff as per the NIPs, though.
Amethyst shows the source for what it's worth: 
Discussion
Thanks for the lead, I’ll investigate.
I have a highlights schema ready for checking highlight events - https://github.com/nostrability/schemata/tree/master/nips/nip-84.
Reading nip-84 though the base spec says “should” tag the source, and “should” use a, e tags for nostr events and t tags for URLs.
Does #devstr have a strong reason to not convert the “should” to a “must”?
cc nostr:npub1xtscya34g58tk0z605fvr788k263gsu6cy9x0mhnm87echrgufzsevkk5s nostr:npub1gcxzte5zlkncx26j68ez60fzkvtkm9e0vrwdcvsjakxf9mu9qewqlfnj5z nostr:npub1jlrs53pkdfjnts29kveljul2sm0actt6n8dxrrzqcersttvcuv3qdjynqn nostr:npub180cvv07tjdrrgpa0j7j7tmnyl2yr6yr7l8j4s3evf6u64th6gkwsyjh6w6 nostr:npub1zga04e73s7ard4kaektaha9vckdwll3y8auztyhl3uj764ua7vrqc7ppvc nostr:npub1n0sturny6w9zn2wwexju3m6asu7zh7jnv2jt2kx6tlmfhs7thq0qnflahe nostr:npub1ye5ptcxfyyxl5vjvdjar2ua3f0hynkjzpx552mu5snj3qmx5pzjscpknpr nostr:npub1g53mukxnjkcmr94fhryzkqutdz2ukq4ks0gvy5af25rgmwsl4ngq43drvk
**r tags for URLs (not t tags)