I guess I’ll bite the bullet and kick off the Tuvix debate.
Tuvix isn’t the first Trek episode to involve transporter hybrids, and it wasn’t the last; but it stands out amongst the Trek fandom and cemented Janeway as a ruthless executioner.
I maintain that the only reason it’s controversial is because Tuvix was more loved than the sum of his parts.
I personally like Neelix, but it’s undeniable that he’s a contender for one of the least popular main characters in the franchise, and certainly the least favorite on Voyager.
Tim Russ is an amazing actor, but Tuvok is a very subtle character. If you pay attention to him, he’s funny and insightful. But if you don’t focus on him, you can forget he exists.
So, by replacing a despised character and a forgettable character with an outstanding character, you’re left with an audience who has no attachment to the status quo.
If, instead, “Tuvix” was built with popular characters, like Janeway, the EMH, or Seven, the audience would have no qualms about a return to the status quo—or at least not nearly to the degree we’ve seen over the years.
Skip ahead to Twovix
The transporter meat blob was dismissed as non-sentient by Tendi, but it clearly had all the intact personalities of its components. Without further analysis can we be certain of that assessment? Why not send it to The Farm™️?
If we come to the ethical conclusion that the transporter meat blob’s very existence was suffering, why restore the transporter patterns to their components rather than their Tuvix’d counterparts? The simplest answer is that they’re more trouble than they’re worth.
No one cares about the meat blob.
No one cares about T’Ilups and co.
Everyone cares about Tuvix.
We let our attachments dictate our ethics then use logic and evidence to justify them.