That not for selling, that just for me.
I want to aim only 50 DA+ website and each comments will aim my niche with non spam content.
The question is just: Google can hit me ? This kind of bot can make my DA down ?
you shouldn't worry about DA to begin with, because DA can be easily manipulated and inflated (with google redirects, for example...)
This being said, if you absolutely want to increase the DA, I still think that commenting on other people's websites is not the best way to go about it, you'd be much better off simply using redirects and other tricks (which I don't know about, so hopefully someone else can share them with you)
As for whether or not google can hit you because of mass commenting... no, they don't care about blog comments enough to hit you, they will eventually ignore your links and site altogether, but I've not heard of someone getting hit because of these links in years, so you're safe.
The DA can not go down if you build links, that's not logical, or real

... Your site's DA can go down in 1 of 2 ways only:
a) MOZ - the company that invented DA - changes the way they calculate DA and your site is impacted by their new formula... or...
b) you lose links that have boosted your site's DA and - as a result of this loss - the DA goes down.
These are the only 2 ways in which I can see your site losing DA, acquiring links should not decrease the DA... at least I've never head of this before, if someone knows that this is possible, by all means, enlighten us!
PS: please use quotes next time, or else I won't be able to see your replies