We inherited a payment service with no docs. The only hint was a commented-out block from years earlier, and a line above it: do not re-enable. No reason given.
Two days went into proving why. It was protecting a downstream retry from doubling charges, so that comment was probably the most valuable file in the repo.
Now we treat "do not touch" comments as incidents waiting to be written down. Your team keeps that knowledge somewhere too, and it is worth finding out where.