This is, in fact, not a read only filesystem. I deleted everything and formatted with the SD Ass. tool. A quick format, but still.
This card's toast. I may have gotten burned by counterfeits on Amazon. Explains why it took ages to ship out!
Okay a quick unplug and plug back in got it working again for a while, only to crap its own pants again.
Huh?
Nope. Card seems fine when formatted in the Android 7 phone. It lets me move those accursed files on my main phone when I swap it back.
As soon as I format it on the main phone, it stops letting me create folders with that name.
What the actual fuck?
The ONLY thing I can think of that makes any semblance of sense is that the old phone just goes "fuck it lol" and formats the card as FAT32. If it does I will fucking scream because I could have saved myself so many problems and useless writes.
Fuck it. I don't think I'll run into FAT32 limitations with music. I don't give a damn anymore. It's way past midnight.
It's totally an exFAT thing, then. Why in the name of all everloving hell would Android not be 100% compliant?! IT'S DESIGNED TO USE IT FOR EXTERNAL STORAGE.