Threads that get started specifically to continue a discussion in a locked thread should ALWAYS be locked/merged/deleted. That's been standard practice for virtually the entire time I've been a moderator (which is running up on 6-7 years now, so this isn't a small sample size). Otherwise the lock power has no real purpose because people will just continue the conversation even after we've locked it down. To be clear, you and Archie are not the first people that have tried to continue a locked thread and you won't be the last. That's what we (or at least I) always do in that situation. You may have thought you were being singled out, but you were actually being treated like everybody else. Not merging/locking would have been the special treatment.
Like I said earlier, I recognize that you probably got hit a little harder than you normally would have because you and Archie were working together and he pushed it farther than you did. There was probably room for differentiated treatment and instead you got universal treatment. I understand that perspective. I hope you understand mine.