"Edge cases" and "conditions" are some of my trigger phrases. Given enough time or users, they are inevitable and passing them off as rare to avoid dealing with them, especially when you're aware of their existence, drives me up the wall.
Unless it's an edge use case you're not supporting, don't sell me your cost avoidance on any production systems.
And edge case is just that though? Something that hadn't been thought of, and makes stuff break, then you can figure out a fix.
I don't know any dev that would agree with "passing them off as rare to avoid dealing with them" - rather, "it's a low priority, but it needs fixing" or "ok, this is an edge case, but holy crap its a bad one"