Earlier quoted context omitted.
I think this is a classic case of familiarity blind spot. It's easy to think of your users as people similar to you, but that's not necessarily the case. Statistically mobile phone users outnumber non-mobile users online nearly two to one, some statistics put the estimate even higher.
This is a misleading reference to statistics without context. It's not a B2C website, and in fact, most of our audience accesses it from Linux devices rather than mobile Firefox. Anyway, even if someone does visit using mobile Firefox, it only takes one zoom-in/ zoom-out to adjust. So it's not really a webpage code issue, it's more about how Firefox renders pages on mobile devices.
No, it requires constant zooming and panning to be able read anything. And this has nothing to do with Firefox, Chrome and other browsers behave exactly the same. It is absolutely an issue with your website.