I can't think of any announcement Nintendo's ever made at an investor meeting that led to the stock NOT dropping. Let's not try and claim that this is unique. 

As for the game, who cares. We're not the audience here, so our opinions here aren't relevant. This is for a similar crowd that Kim Kardashian game that makes $50k every day. This is meant to easily test the waters while making a killing at the same time. 

The moment Nintendo announced DeNa partnership?

I wish there was an option for maybe, but im gonna go and say yes its a good idea. Because first off  i see Miimoto as nintendo's facebook but really with a Nintendo twist, with not only social interactions but also games and customisation, and its not this cheap customisation. I think it can be huge. Where i think it will be the biggest though is Japan or mostly japan females. Thats where i personally think it will strike the most. Also im personally glad its not a huge Nintendo Ip because i didnt want a big Nintendo ip to be locked behind microtransactions. But i have to say when i first heard of it i got a little bit dissapointed, but now i realised for what it is and gave it a bit more thought. I wont be quick to judge this time around

You have said very well what I believe.

A lot of smart people said that about Todomachi Life. But UPS...

Basically I view Miitomo as Nintendo putting their foot in the door in regards to the mobile world. It has a simple premise and looks to be popular in the market that Nintendo is aiming this particular game in: Japan. It's also there so people can sign up for their My Nintendo accounts with ease. Making the jump to NX smooth as can be given that it looks like such accounts will encompass the core of NX itself.

Also the stock market is a fickle mistress. The investors are just pissy because Miitomo is going to have little if any impact on this fiscal year. They will more than likely come back if this game proves to be popular enough.

In the end: Miitomo is a great idea. Get people in with something basic and get them involved with having a My Nintendo account (by way of benefits and other goodies) and then have them stick around long term with established IP mobile games later on and even mobile specific new IP.

And before people overreact I'm not saying to put the next "Splatoon-level" breakout on mobile but something basic like Rusty's Baseball or something like that.

I legitimately think its genius. And I think you're right, it'll have mini games like the ones you describe. The mini games will have a big social aspect. Like I said since March, think Words with Friends or Draw Something.

Interestingly enough, stocks weren't traded for Nintendo the day they announced the DeNA partnership. It seems like that was one guy buying a lot of stock right before the day closed, not counting Nintendo and DeNa buying stock in one another. 

That might be the only time their stock (technically) rose in recent memory after their quarterly meetings or after big announcements. I think it dropped hard the next day though, if I'm not mistaken, once it opened back up for trade. My point is, never trust stocks with Nintendo. They don't say anything more than that their investors are ignorant of what Nintendo lives for. 

Looks like some quality of life enhancing software, which I'm okay with, I'd rather have them build that solid network accross platform than making a full gaming experience on smartphone. This is not a let down on gamers.
This clearly shows they have defined their plans well.
I thought I'd be disappointed by their first mobile move, but nope, they surprised me in a good way.

kinda a meh... will wait and see though.