Nice of you to say as much Hikermor. Mighty big of you.

Tying Swiss seats, the norm before the sewn seats were widely available, and a major step up from the venerable swami or bowline on a coil, uses a square knot for the final knot. It was backed by a half-hitch on each tail. It had been tied that way for roughly 80 years before I learned it.

Square knots are okay but they need to tied correctly, dressed, and backed up. Failure of any of those steps can be catastrophic. Square knots are good but you can't fudge it and get away with 'close enough'. It is one of those knots where it is either absolutely correct or an invitation to disaster.

For joining ropes in climbing I have shifted to a Flemish knot, essentially a back-fed figure eight. (Not to be confused with a double figure eight or, ominously named, the EDK.) The Flemish is robust, easy to tie and untie, and tolerant of both abuse and inexperience. Novices can easily handle a figure eight and back feeding the other line to match is intuitively obvious. Errors stand out so they can be corrected.

The current favorite with rescue workers for joining lines seems to be a fisherman's knot with three wraps on each end. It is a solid knot with a lot going for it.