"Crimp links which have been properly re-insulated with heatshrink or self-amalgamating tape don't need to be inside a junction box".
According to the NEC all 120 volt connections are to be made in a junction box or conduit body. Connections can fail so the connection must be made where it is accessible and repairable while minimizing fire danger
. Never splice AC outside of a box!
Yes there is self fusing tape but good tape such as 33+ or 88+ will fuse in time. It does not come off! Cheap
tape that fails is what you get when you are not willing to pay the price
. Vibrations causing wire nuts to fall off on a sailboat? Come on, now! Wire nuts torqued properly don't often back off and don't move at all when secured by tape. There are many methods of tying two or three wires together and there are better methods perhaps than the wire nut but the wire nut is universally obtainable and works well.
If this were on a piece of machinery with high levels of vibration such as motor
leads I would use copper connectors such as the Kerney, wrap with cambric to prevent sticking, wrap with rubber to insulate and then wrap with 33 + to waterproof. But this is a little splice in a box on a boat.
I am a great fan of shrink and self-fusing tape, having used it all and will again at times. I am not too much a fan of the insulated connector, finding that a non-insulated connector gives a better connection, no matter what the tool used, for the tool does not have to compress the insulation
to mechanically make the connection on the un-insulated connector.
I use a Sta-kon type of crimper on smaller non-insulated connectors, coat the connector with scotchkote after the crimp and then heat shrink over whole works. These connections are quite well enough insulated for 12 or 24 volts, much smaller in physical size than the insulated ones and can be color coded with the applied heat shrink.
Perhaps using adhesive
shrink would be faster but I like my method and they have not failed on any marine
application I have used this combination on.
Again, it is not about dogma, it's about thinking. I see way too many absolutes espoused here when the poster only understands part of the whole picture.