I've heard, and maybe it was discussed here, that burying them TOO deep can lead to mold, fungus and stem rot. Is that only an issue past a certain height?
Iv have never heard of that happening just from burring your stem to help cut the stretch out
Im not saying that it can not happen , im just saying iv never heard of it happening
As far as seedlings goes its definitely not a problem ,
If you got a seedling / plant that is ( lets say 3 to 6" ) and its stretchy / skinny / scrawny as hell then their is absolutely no problem re burring it up to the cotyledon leaves
If it is so stretchy that the true leaves are like an 1" or 2 from the cotyledon leaves then i would even bury the cotyledon leaves and bury up to the first set of true leaves .
But i would cut / pull the cotyledon leaves off before i do it though ,
But thats is just me , you do not have to cut them off ,
Your buried stem will still grow new roots anyway .
But as far as burring to deep that it gets mold or fungi , iv personally have not heard of that ,
But im not burring up to sets of nodes at a time though ya know ........
P.S
Don`t forget to lower your lights afterwards !