Minion Pro composes accented Greek uppercase letters (e.g. Ἓ or Ἧ) anchor-like: The base glyph keeps its position and the accent is added to the left. However, these glyphs will protrude beyond the left margin when they are typeset (the following HA's are aligned left):
(left: Minion Pro, right: Segoe UI)
Many fonts (e.g. Segoe UI) shifts the base glyph to right in order to prevent such protrusion.
What would you recommend: Going the Minion Pro way or going the Segoe UI way?
(What are the advantages of the Minion Pro way?)
Check out more recent Adobe fonts with polytonic support, e.g. Arno: