You may not be an electrician, but good eye. Yes, somethings not right. But it's odd, usually it's fuse 14 which has A/C and the aux fan on it. 12 should be an 8A fuse with the radio, taillights and a couple of other low draw items. An 8A fuse shouldn't get that hot, although it's not that melted like 14 can get where the fuse tabs are so separated the fuse hardly makes any contact. Unless maybe a big, BIG stereo/amp, the fuse kept blowing and a 16 or 25 was put in there.
No it's not perfect, but really compared to what I'm used to seeing on 14 it doesn't look bad at all. I'd put an 8A in there and see what happens. It might blow, but fix the problem if it does, don't just put a bigger fuse in there.
Might be late on recomendations for melting fuses and wires...but I am new to the board. My Bimmer is a 1980 E12, 528i. I said goodbye to the old "ceramic bullet" fuses and installed a holy grail blade fuse module. A bit of work, but not too rough to do. No more loose fuses and works amazing!