cote - The fact is that you don't know what a 6 month old baby thinks, and you don't know that anyone has "actively harmed" their baby by sleep training them under 6 months.
All that is just your opinion.
Others have their own. Like seeker, my opinion, is backed up by research of how infant sleep evolves throughout the first year of life and continues to evolve quite significantly up to about the age of 3.
When Ferber published his sleep book in the 80's most of his guidance pointed parents to practice sleep training from no younger than 6 months.
The new Edition of Ferber's book (a couple yrs ago I believe) now seems to point parents to not practice sleep training till after 12 months.
Of course, it is your child and you do as you seem fit. It is only fair that other people know what current thinking is and to do their own research and make their own decisions as they see fit.
Just because it seems to you that it has done your child no harm doesn't mean that your experience will be duplicated elsewhere.
OP, good luck with whatever you decide to do.
Can I suggest you putting your baby in the pram, take her in whatever room you have to be working in and shoggle her back and forth / side to side to get her off to sleep and to keep her that way? If you put a slipper under a wheel or two, it imitates the cracks in the pavement when you shoggle the pram back and forth.