As RickDeckard showed off, it's a new way to break up the address and use bold formatting to make it easier to verify "block by block," if you will.

You can read more on the motivation and standard that was proposed by the Bitcoin Design community here:

https://bitcoin.design/guide/glossary/address/#visual-formatting

We've also deployed the new address display format in Envoy as of v1.6.0 (in beta!) so that verifying addresses visually between the two is even easier!