Originally Posted by
Amesja
Safe spoke tension has much more to do with what the rim can withstand than "when the nipples round off."
Run too high a tension and the rim will crumble as the spoke holes crack and deform.
IME only the lightest rims start doing it hard before the nipples do, but of course YMMV... and if a light rim deforms from too much tension, congratulations - you found the limit. Back off half a turn or so and enjoy.