Songs have been disqualified straight away in the past after discovery of former participation in NSC
(Streets ET NSC 17, if you want a precise example xD)
They
weren't allowed continued participation; the entry was changed.
The difference between then and now is that that instance was noticed almost immediately, with ample time for the change to happen.
Giving Tohru the opportunity to change is still technically an option, but it means that everyone (both semi and reju) who has voted in Semi 2 will have to potentially change their votes to accommodate the change. We'd probably need a deadline extension for that.
If the song is just removed, only the people who actually voted for Tohru will have to add in an 11th placer.
It's an awkward situation, but it would ultimately be more unfair to allow its continued participation... It would be unfair on Comino, who already sent the song that was rightfully their own, and it would be unfair on other Semi 2 participants, who are being put up against a song with an established position within NSC already (although it came 11th in the semi in NSC 48, this would be a lot clearer if it was a winner, for example)
While we don't want to punish Tohru for something he wasn't expected to know, removal from this semi at this stage is the basic necessity unfortunately. We will be prepared to offer some sort of compensation for Tohru in NSC 58, which will be discussed in due course. Sincere apologies to JackBauer of course, who's had to go through this unaware
When you come online, I hope you don't feel too angry; feel free to PM one of the mods to discuss the situation and what can happen for you in NSC 58
This is my take on the situation anyway...