Janet,
This eating a lot at night is a normal phenomena in human babies that I have
seen termed "cluster feeding".  This is part of my anticipatory guidance for
all moms, to expect this and use it as a time to relax before bed.  Many
babies also do it in the early morning, but mom does not mind as much.  I tell
moms that the baby seems to need to 'tank up' for the night, and should then
sleep 4 or 5 hours.  It may be related to hunter-gatherer patterns of human
living where people worked in the day, ate, and then sat around the fire at
night talking, singing and dancing.  This is a convenient time to feed baby as
well.  Daytime feedings in these societies seem to be short and frequent,
without interrupting moms work.  At night there is time to relax and enjoy.
As for formula making babies sleep, the amino acid composition is soporific,
and formula is not efficiently utilized by the body as fuel (baby is actually
getting less energy out of it ) which according to some researchers (Zeskind
especially) is not good for human babies, predisposing them to SIDS. My theory
on things that worry people:  reframe it so it is expected and some purpose is
seen in it and it will be far less threatening.
Hope this helps.
Catherine Watson Genna, IBCLC