The XML files contain many spelling errors. See Planet "Sarrow" in PlanetDefs.xml for example - which should clearly be "Sorrow" given the other planet names in that system.

There are also inconsistencies in naming conventions - some techs have "Tech" stuck on the end of their internal names while others lack that suffix.

Another issue:

DefenseSystemTech for Defense Systems

WeaponsSystemsTech for Weapons Systems

Note the inconsistent plurality. These should have been:

DefenseSystemsTech for Defense Systems

WeaponSystemsTech for Weapon Systems

I know a girl named Pheobe.  It's on her birth certificate.  Same parents maybe?

30 second search with Notepad++.  It was the first that I saw.  Note the misspelling that I missed in the same line.

ImprovementText.xml   

<Label>AscensionGate_ShortDec</Label><String>When completed, alows a race to reach the next plane  of existance.</String>

ThalanTechDefsText.xml

<Label>ThalanSingularityDrivers_Dec</Label>
    <String>The pinnacle of kinetic weapon technology, these launch micro singularities that collapse into existance shortly after impact. These are bad news, the worst news really, for anyone who can't get out of the way.</String>

Mass for a lot of components is similarly exaggerated in the tooltip versus what actually gets consumed when you use the component. On a Tiny hull, a Durantium Composite Armor defense module shows 11.5 mass would be consumed, but adding the component only adds 5 to the design.

I do have various miniaturization techs; perhaps the tooltips don't reflect the component miniaturizations?

dgcustomerfirst

ImprovementText.xml - They start at <Label>XenoFarm_Name</Label>

Edit:

Base Game only. (Data\English\Text)