I was asked recently by @netto.eth to help him debug an issue with primary names not being displayed correctly on Etherscan. Ultimately I ended up building a new tool for ENSWhois - Primary Name Debugger | ENSWhois.com
The tool allows you to enter an address and discern if the appropriate forward and reverse records have been set for spec compliant primary name resolution.
The tool gives consideration to both ENSIP-3 and ENSIP-19.
This is a first pass - there is a lot of nuance to backwards compatibility of reverse resolution specifications especially considering ENSIP-19 and cases where forward resolution uses custom resolvers (often also going off-chain). Any feedback is welcomed.
Etherscan Issue
The specific example I was debugging is the primary name resolution of the address 0xd2f7497bfe2daff1a69f306036a036abc8154aeb which is correctly setup (backward tx, forward tx) as ens.relayer.blockful.eth.
Etherscan does not display the primary name on the associated address page. My best guess is that they run their own indexer for primary name resolution and do not respect the default cointype - 0x80000000 (2147483648).
Assuming my hunch is correct, for the time being, the simplest solution to have your primary name display correctly would be to explicitly set the chain-specific forward resolution for your name (rather than taking advantage of the EVM chain default). Ethereum Mainnet is cointype 60.
Pinging @mely.eth @gregskril - it may be worth reaching out to Etherscan regarding this. I am going to iterate on this further when I have time and could offer a stable API endpoint to support future integrations.