So I recently tried the Riftborn again after buying Supremacy and trying out the Hissho for the first time. One of the things I noticed as Hissho was that my planets kept unexpectedly losing population -- it turned out that Hissho have technology-unlocked empire bonuses to pop limit on sterile worlds, so as I was terraforming, the pop limits on my planets were dropping before going back up as I terraformed to fertile worlds.

Riftborn are another faction with a very obvious and pronounced preference for sterile worlds, and far moreso than the Hissho (for whom it's presumably an ascetic thing). Yet, Riftborn have no particular bonus to pop limits on sterile, nor any particular penalty to pop limits on fertile, despite having the unique ability to terraform planets away from fertile and to sterile. This puts them in the very strange position where terraforming planets to ideal habitability will always cause the pop limit to fall, which on very full systems will cause some pops to be irretrievably lost.

Now you may say "but sterile planets give better FIDS, since Riftborn don't use food reversed fertile/sterile pop limits would be overpowered". And ... yeah, okay, that's pretty fair, but consider that food-based empires have fixed growth thresholds (150, 300, 450, 600 depending on game speed) that don't rise as population rises, but the Riftborn already have a scaling cost per pop. If that scaling was just increased a bit, then the exponential growth from huge lava planet industry could be levelled off a little. Also it just really feels horrible to lose pops whenever you terraform, and doesn't make sense from a lore perspective either. It would also maybe be good if the empire-wide happiness bonus/penalty for sterile/fertile was changed to a bonus/penalty on Riftborn pops so you can't for example fill your lava planets with Imperials who are inexplicably content with the situation.

I just really don't enjoy the Riftborn as they are now. It feels jarring to play as them.

G2G balance mod adds these changes:

Riftborn:
- Biophobic trait will now add population slots on sterile and remove some on fertile
- Population cost for Riftborn now also scale on the empire-wide number of populations
- Added A star system improvement and an emprie improvement to add population slots on Sterile planets 

Expect these to be impleneted in next release.

Sublustris wrote:

G2G balance mod adds these changes:

Riftborn:
- Biophobic trait will now add population slots on sterile and remove some on fertile
- Population cost for Riftborn now also scale on the empire-wide number of populations
- Added A star system improvement and an emprie improvement to add population slots on Sterile planets 

Expect these to be impleneted in next release.

That second one seems questionable depending on implementation, hard to get new systems rolling without bringing in a minor pop at some point surely. But the "use one system to produce rifties for the whole constellation" strat, while interesting, is probably degenerate in it's own way so...

@OP: I agree that it's a thing, but rushing that science tech that lets you build a +1 pop on sterile building offsets it decently, as does shopping around for the ideal planet type to terraform to as a function of FIDS vs pop loss. I think I settled on Arctic for science last playthrough, for example.

Well, later change states that

Update: 8 Oct @ 5:49pm

5.3

Faction balance:

- Restored Riftborn creation industry cost to its former value

That's why I linked whole page, but quoted only relevant block