It's stretched more then I'd be comfortable with. The danger is that if the soil gets dry the stem won't be able to support the leaves and the plant bends over. If that happens and isn't caught soon enough it can kill the plant. The stem is to fragile to tie a stick to it, so burying would be your safest option. The stretching is always lighting related. Sometimes it's because it was pre-germinated and didn't get light quick enough and other times it's because the lighting is set to far away.
The way I've eliminated this from happening is by not pre-germinating and instead by sowing into a small container filled with soil and leaving the lighting on 24hr. It waste a bit of electricity since the plant doesn't need the light on until it sprouts above the soil, but I found by leaving the light on the seedling gets lighting the very moment it needs it.