Ideas:

1. By systematically comparing the degree of variability among glyphs belonging to what evidently is exactly the same type of glyph I have noticed that this type of glyph very seldom shows any variations. And if there is a variation it looks like a sign.

I therefore interpret this 'special' quality of the glyph as indicating a God. You cannot talk or write about a God without using the exactly correct forms in pronounciation or design. Or you would risk to be severly punished by the Power offended.

The prominent position of this glyph in the texts of rongorongo makes it probable that the God indicated is the Sun-God.

2. However, this glyph might possibly sometimes be used not to indicate the Sun-God but instead to be used as a symbol for a Power straight up in the sky (in contrast to a celestial Power occuring near the horizon only).