I have always watered from the top and have never had any plants damping off. I start my plants in a sunroom where the air temperature is about 73° rather than in a cooler area like a basement like some people use.
I also use a sterile soiless mix and brand new cell packs since I only grow 2 trays of seedlings and the cells are only $99 for a whole tray.
Fungal spores (like the ones that cause damping off) love cool and damp and they can be introduced by fungus gnats, used pots or garden soil and they will thrive in cool, moist conditions whether you water from the bottom or the top. I try to avoid all of these possible routes of transmission.
Additionally, if you are bottom watering and the water is shared by all of your pots then you could also be spreading the spores if they are present on some of the pots. They will float to the uninfected pots.
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