After a few weeks of confirming its fondness of cat food, I trapped it in a cage with cat amenities, tried to pet it and got bitten.
Transcript
Scared and alert fluffy black cat on a perch in the upper corner of a big cage, at eye level with me and camera
First of all, how is the bite wound doing? Cat bites (and scratches) can transmit some very nasty stuff, and it's often recommended to see a doctor ASAP. I had a bite a few years ago that resulted in me getting IV antibiotics.
In terms of winning the void over, patience is key. Let the cat lead any future physical interactions. You can offer your finger for it to sniff, and when it decides it trusts you, it will rub its cheeks against your finger. Talk to the cat in a calm voice. Just talk about anything, read to it, etc. Look up "slow blinks" and learn how to read the movements of its tail. If it's tail is flicking, back off. Jackson Galaxy is a great resource.
Have you been able to check it for a microchip? Have you checked to see if it has a human family that might be looking for it?
The wound was shallow thanks to gloves and it is almost healed; I thoroughly disinfected it ASAP of course, with lots of scrubbing, water, alcohol and non-alcohol disinfectant.
No, I can't check for a microchip unless the reader works from a foot away (most are cca 2 inches), which would allow me to place it close to the food bowl. I could try to trap it again and check for sex etc., maybe even use a phone or generic RFID reader. It will indubitably get mad at me and I don't know if welding gloves will be enough to prevent more scratches.