My cilantro seedlings have grown a lot of true leaves and the cotyledons have grown big. Can I cut off cotyledons? Do they fall off?
In most plants the cotyledons fall off at some point, in others, they shrink, shrivel and dry out.
There’s no need to cut them off and I would discourage you to do so while they are still green - green means photosynthesis and feeds the plant. Plus you‘d be creating a small wound, which will probably just heal fine but a small risk of infection remains. If your cilantro seedlings are larger and a bit intertwined (as happens so often), you’d probably be crushing the cluster of plants a bit. But without a photo the individual situation is hard to judge. (I do remember your earlier post, so based on that, I’d rather say leave them, they are are still needed.)
In short, I wouldn’t bother.