In regards to complaint 1, do you happen to have the toggle for "beautiful images" turned on on the phone? If so, that is why the inbox looks dark (really a smoke grey color). I thought it was a bug as well when I first used the app, until I tested with "beautiful images" turned off. The transparency setting for the background for the "beautiful images" is what causes it to look that way. It looks normal on iPad and Mac, because there is more screen real estate to display with background image, whereas with the phone it is still there; albeit we can't see it.My first message to support over their "chat" was 13/08 and heard nothing back. That alone puts me off them as the customer service with Newton was lightning quick... I'm trying both Spark and Airmail at the moment, it's quite close to be honest.
I haven't had a problem with rendering yet, where the text is cut off etc.
In regards to the toggle of the "unified box," I have been able to turn it on and off at will, and still be have the "unified box" feature available.
Read receipts have been pretty consistent for me, barring someone possibly preventing the alert trigger.
As to icons, they do look smaller than Airmail, but haven't noticed any looking flat. That would be irritating to look at, if one had several with that problem.
I haven't messed around with the Aliases feature, yet.
I wil send out an email to tech support, and see what happens (if anything). Customer support not getting back to you within 24hrs is unacceptable, especially when you are a paying customer.