When do I get to rate a Mii fantastic?
In my experience, you get rating opportunities if one of the following three things occur:
- The second time you meet someone.
- When you meet someone you've met before and they've changed their hat.
- An unknown criteria when you meet someone past the max number of times (currently 999). This one seems to have a pattern (maybe every 10?) but I don't know what it is.
My understanding is that you can only rate a Mii as 'fantastic' after you've previously seen it at least once - the first meeting doesn't allow a rating to be given.
If the 3DSes are passing through the same place repeatedly (as mine does since I take it on the train to work) then you're perhaps more likely to meet the same Miis multiple times and therefore rate them.
You are able to rate a person the second time you meet a person's Mii. If you rate them "Fantastic!", then they should receive that rating on the third time you meet them.
If their Mii changes their appearance (e.g. wear a new hat), then it allows you to rate them again. However their Mii can only receive 1 "Fantastic!" rating from you.
Now I have heard that if they change their StreetPass Mii for a new one (created in Mii Maker), then you can rate that new Mii on the second encounter and they will receive it on the third encounter (i.e. getting a second "Fantastic!" rating from you). Note: Having not seen that myself, I don't know whether changing your own Mii would also let you give a second rating to someone's Mii. I'm guessing it might work though.
Credit from Gamefaqs: silktail