I don't think Kanon's head writer (Naoki Hisaya) was ever involved with Tari Tari, there was evidence that lead to speculation he might be but people (including me) jumped the gun on it.
Hisaya has been involved in a number of works since Kanon: a VN called Moon Childe, Sola (you do know this, right?), a novel series called Sakura Kagura, and an anime slated to air this fall called Sora no Method.
Sakura Kagura was published by Infinite (or was it? I can't find evidence of actually being released online... this turned up in the search but then I realized its another author's book), a production company that has also been involved with Tari Tari, Nagi no Asukara and Glasslip (and one non-PA Works show... Da Capo III), and, interestingly enough, had Hanasaku Iroha's character designer as its illustrator.
The speculation/confusion came about because Infinite announced that Naoki Hisaya would be working on an original project for them shortly after Tari Tari was announced, without announcing what that project was.
(BTW, a thought just occurred to me? You know how the bondage stuff in Hanasaku Iroha's third episode was modelled by a male employee of PA Works? How much of Okada's emasculation phase coincides with her having contact with PA Works? Maybe this stuff went two ways.)
I just call any long posts tldr. Doesn't mean I don't read them, unless if its written by people I don't care about.
I don't know, but I really dig the character designs this time, unlike Tari Tari and Nagi no Asu Kara. Tari Tari had the most bland and boring whilst Nagi no Asu Kara had the most exaggerated and over-cutesy, particularly Manaka and Miuna.
Nothing wrong with big eyes though as long as it doesn't reach Visual Arts Key levels. And yes I can't help being excited, but thats because I fall under the definition of fanboy for that studio.
Also, I stole one of your phrases for my latest post ("it caters to me" and therefore I give 0 shits )