Is my main panel improperly bonded?
It's bonded, alright
Meter-main boxes like yours have their neutral bars permanently bonded to the case at the factory, and thus have a notation on their label saying that they are &quot;suitable only for use as service equipment&quot; (emphasis mine).  In your case, this is done through the mounting of the left-hand bar; if you look closely at it, you'll notice that there is no insulator between it and the case, unlike the neutral bars on a typical loadcenter, which are mounted on insulators (whether they be part of the backpan the busbars are attached to, or separate standoffs).