Kragnost
The parser cannot handle (does not list for addition to the data.cfg file) a planet if one already exists with the same number.

For example:

Nexus (98) has Einstein (325)
Twinkle (103) has Steel (325)

If you already have Einstein (325) in your data and then parse a system map of Twinkle, the parser doesn't give the option to add Steel (325) to the data for Twinkle.

For celestial bodies, the unique identifier for the "thing" is the number + the system its in. This differs from (all?) the other game data as everything else is a unique number I believe.