"Twisted and taped" does seem pretty secure, electrically, if done well. That is not how I would do things but I removed dozens of splices made that way when I ripped out all the previous owner's work in this house and it was at least 20 years old. (dating from a 1978 remodel as best I can tell) I didn't find any traces of heating, even on the 1440w bathroom heaters.
