Retaining a dot on the letter "i"
Sometimes people (or language communities) wish to retain the dot on i even when there is a diacritic above the āiā. This should not be part of the behavior of the font. Unicode clearly states that the dot should be removed. See Chapter 7 of The Unicode Standard. You should encode it as U+0069 U+0307 U+0301.

There is a similar expectation for j .
This article formerly appeared on ScriptSource.