Quite fair; my issue is not that bad outcomes shouldn't be possible (I always endeavor to do the same). Rather, in the context of the preceding conversation, the principle given was some variation of "Don't take away the things that make the character matter to the player." I fear I don't remember the exact wording, so that's a complete paraphrase, not the original wording, but it gets to the same point.
I certainly grant that for some styles, e.g. "classic" ones, there isn't any particular thing, and having the character taken away is just an expected part of the experience. I would also say those classic styles are...not as commonly-played in "contemporary" gaming, because they don't appeal to the average contemporary gamer. For players of more contemporary tastes, rather than classic ones, there will usually be certain things that are very important to their investment. Where losing the character entirely would actually be less of a problem than losing some particular thing about said character. For example, perhaps a 5e Fighter who picks up calligrapher's tool proficiency and uses those tools to add new poems and illustrations to a book that's been in his family for three generations. To have said book just get casually burned up because (say) the character got hit by a fireball and that spell can set things on fire...sure, it would be a very small gain of verismilitude, but it would ruin an irreplaceable key element of the character's roleplay, for pretty light and transient reasons.
Now, obviously, this could theoretically be be abused if you have a player acting in bad faith, but as I have previously argued, if we are to assume GMs acting in good faith, then I expect a presumption of good faith from the player unless and until evidence suggests otherwise. It's a give and take; the GM gives those minor, incidental deflections away from absolutely perfect verisimilitudinous representation (such as "random fire spells won't burn your family heirloom book"), the player gives that such deflections will only apply to a few, limited, warranted things, and would be lost if the player actively does something to risk them (and presumably none of the items will have more than highly incidental mechanical significance.) Basically, if a player really cares about a "fluff" item that might be conceivably vulnerable, don't just willy-nilly let it go kablooey simply because it would give a very minor boost of verisimilitude; conversely, the player should understand that taking obvious stupid risks with a treasured item might result it in being destroyed.
Tit for tat. Respect given in both directions.
Or, if I may, consider: You play a Sorcerer. Your group went through some kind of planar adventure and interacted with a cousin of a rust monster that feeds on magic instead of metal, and the thing almost killed you in a fight, but you survived. The GM says, "Well, because it fed on your blood, you've lost all of your Sorcerer magic. Replace all of your Sorcerer levels with Rogue levels, unless you accept a Warlock pact from some empowering entity to fill the void--then replace the Sorcerer levels with Warlock levels instead." Would you find that a reasonable or appropriate thing for the GM to inflict on your character? Would you feel that something pretty essential to the character's nature had been rudely ripped away simply because the GM felt that that would be "more verisimilitudinous" than just having your character recover normally from their wounds?