Thanks Jerome.
I've disabled caching for now but the main issue is I don't know where to look for this HTML comment. I've tried different browsers (Chrome, Safari, MS Edge) and none of them appear to show these comments. It's very frustrating. I must just be looking in the wrong place.
I'm not going to copy and paste PHP around because I'm concerned about messing up the UPS plugin or failing to call writeToLog correctly.
Each step is done with ajax calls, is that why I don't see it in the develop consoles? I'm just at a loss.
This is all in service of trying to fix my ORIGINAL issue,which is that rates are really out of whack compared to the exact same package quoted from UPS.com (only using weights, no package dimensions on either system.). I know, I know, you just hit UPS's webservice for rates but there's obviously something different about what HIkaShop is sending versus what I'm filling in via UPS.com's forms.