Here is your occasional reminder that doing the long-tailed cast on over two needles is fine! Not mandatory, not forbidden, but fine.
The trick is knowing why you would want to do it and only doing it when it’s appropriate.
Casting on over two needles does not make your caston stretchier or looser. To do that either pick a cast on that has more stretch (you can google ‘stretchy cast on’ and experiment with different options to see what you like best), or leave more space between the stitches of your long-tailed cast on.
But casting on over two needles does make the loops of yarn that make up your first row of stitches bigger. And if you’re a loose knitter (me!) but a tight caster-oner (also me!) then sometimes the loops of yarn from your cast on can be smaller than the loops of yarn you usually make while knitting, which can make your first row all bunchy. And casting on over two needles does fix that.
So I do it! And it’s great! Because I know what it accomplishes (making my first row of stitches the same size as the rest of my stitches), and I am using it intentionally.
If you don’t believe me, do an experiment. Grab two different colored yarns, tie them together, and put one color on your index finger and one on your thumb as you work the long-tailed cast on. (Some day, when I have free time and the requisite amount of motivation, I will do this and take pictures and explain it all. But today is not that day.) You’ll see exactly what’s happening and all of a sudden it will make it make So Much More Sense (and then you can explain it to anyone who lectures if they see you casting on this way).