The only time I sell nanoforges and synchrotrons is to fuel the infinite money bug with my colony's Commerce industry. After that gets patched, they will probably sit in storage to rot in the slim chance I need them later.
I would not mind making corrupt nanoforges rarer if that means making better items like pristine nanoforges and elite blueprints more common, which are already too rare. I can explore and dig up half the sector (with salvaging and tech mining) and not find a pristine nanoforge.
Making them rarer though would help to stop them from being something that's a must-have once, and then becomes vendor trash.
Too rare just makes them too annoying to find. You still need or want them whether you find one or not. Rather have too many than not enough. Too few, and you simply raid core worlds for it, which is what I did for half the games for pristine nanoforge, due to it being too rare. I rather find them early when I can make use of them after I build a colony, instead of too late after I effectively won the game. That is big problem with colony production now, the game is practically over by the time I can build what I want.
For what it is worth, I never sold my survey data thinking that if I did that, whoever I sold it too would pop-up a colony at some class V world I want to colonize later. For example, find a class V Terran I want to claim and sold the data to Hegemony? About a month later, new Hegemony colony pops up at that planet. Or if I claim it first, they send an extermination fleet to sat bomb my colony away. Seeing that all of the data stack, I doubt they remember the location, and selling data is safe.