[Herald1360]

Since the 78L05 is commonly TO92 plastic, its thermal resistance junction to ambient is quite high. I found 230C/W buried in the datasheet for the 78L series. Tj max is 125C, so in 40C ambient (not unreasonable inside a bit of gear) max Pdiss is just under 370mW. In 25C ambient, this creeps up a bit to just over 430mW. That limits 100mA operation to less than 4V differential. The SO8 version does a bit better at 130C/W J-A.

I wonder if some ripply 78L05 supplies are just self protecting?

Just because a device has Imax 100mA and Vin max 30V doesn't mean it can handle both at the same time, though at least the 78L05 (probably) wouldn't blow up!