Alright, the answer has been revealed.
The character style, in advanced character controls, was for some reason set to 106% vertical scaling.
Credit to Uwe Laubender on the Adobe forums for suggesting checking that.
I don't think this is enough for a real answer, but it feels like it shouldn't be a comment…
The main issue is I don't know what it's trying to tell me.
Until I read the reddit page I thought it was a beach & ocean map segment.
Aside from the fact that an iceberg looks weird with a sunny desert sky, they're rather famously 9/10 underwater.
The fonts ...