[quote=@Raineh Daze]Exact quote: "By slaying countless monsters, the sword has taken on magical properties, and can now harm magical beings that can't be hurt by mundane weapons". It isn't explicitly negating [i]any magical anything[/i].
[/quote]

This is semantics. According to [@IncredibleBee]'s interpretation of Guts, the Dragonslayer harms magical things. Interpreting that quote as "Dragonslayer can harm magical things only if they can't be hit by mundane weapons" is [i]really[/i] reaching. Beyond that, something like the Dragonslayer would most likely sunder a pickaxe like the one this nameless character has, regardless of whether it's got an enchantment or not.

 If it's enchanted to be unbreakable by mundane weapons, then logically the "anti-anti-mundane" effect should take effect.