Do you feel that maybe you are losing sight of your lemmy.nz communities in all the noise of federation?
A good little search trick is to search as shown below. This will pull in all the threads on lemmy.nz (or no.lastname.nz) if you are on a larger lemmy instance:
I think the suggestion is for people who made an account somewhere other than lemmy.nz, who want to find posts on lemmy.nz. We have lots of users here who made their accounts somewhere else (think about how you can make an email address anywhere and still communicate with anyone who has email).
In fact the tip @BlueEther@no.lastname.nz posted can be helpful for anyone, as it will help you find content on both lemmy.nz as well as other lemmy instances with a .nz domain (such as no.lastname.nz or feddit.nz).
Yes, not overly useful if you are registered on lemm.nz, as you can use the local function. For people that are not on lemmy.nz (myself included) searching on the domain can make finding content easy