I went to the demo page you referenced above, using MAC/Safari, and set it to PasteText. I then copied and pasted this exact HTML:
"Climb if you will, but remember that courage and strength are naught without prudence, and that a momentary negligence may destroy the happiness of a lifetime. Do nothing in haste; look well to each step; and from the beginning think what may be the end
from another site.
When using MAC/Safari, the font tags are not stripped. When using Windows/IE7, the font tags are stripped. Please try this in Safari and see if you experience the same behavior.