Re: traces, via: I don't know. We only 1 Uno, it is secured onto a wheeled platform at the moment, I can't see the bottom to see if the vias connect to anything.
Re: the trace wiggle - also not important at the speeds being used, even at 230400 transfer speed the impedance would not be that critical.
I am a bit confused. What is the purpose of having 1K resistors between '328p and 16U2 when we can have interfering signals if there is both USB(-to-serial or vice-versa) and external (shield serial in and out) activity ? Can you explain this in more details ?
Anyone have any further insights into the track wiggle (both tracks are not equal in length and after reading the impedance-controlled routing article, I felt that making tracks/wiggles longer is worsening the signal integrity ??) and the missing via holes along M8RXD and M8TXD tracks?