I think the thing that reminds me that this is a user-controlled story with user error is when world building falls apart. For example, unless your character is a first year muggleborn, they probably know the Potters, the Weasleys, the Malfoys, etc. Especially if they are same house or close to the same year. So I'm immediately taken out when a canon isn't recognized. That, or if a character is in the same year and House and they find themselves introducing....
Now, I know I've done stuff like that before on accident, so it's totally not unforgivable. It gets difficult with grads, especially if you are in a rush and don't sift through apps to double check. I usually try, within the context of my reply, to find ways to gently remind. Something like mining steel, I'm not sure, because I'm sure it would just come off as passive aggressive, as there is no way for your character to play along with something that... can't happen. PMs that come off as sincere in trying to communicate the gap in information, I'm sure can help. The other method I employ regularly... "I know what they were getting at... Let it go." That one's hard. But it's probably the most effective at keeping myself from going insane or getting into drama.