That if people were to email press@adafruit.com with a subject line (for example) of 'FLUX - AMA for later', these questions could be rounded up and the responses could then go onto a Adafruit blog page later, when and if applicable?

Couple of tweaks though, try to avoid the same call for response, '..is that right?' or whatever. Patterns in speech become REALLY old REALLY quickly.. It can start to create a picture in their head that this is staged (and it kinda is) which then starts to cause them to raise walls up. Keep to the context of the question using whatever words you're comfy with 'X...? I got that right?', or 'soooooo... X yeah?' and they'll spot the pattern but because of the conversational nature of it their hackles will take a lot longer to raise.

The other thing is putting pauses in. Yes pauses are remarkably powerful, actual dead air forces the other side to fill it, but it also creates a pressure vacuum, it FEELS like minor bullishness and can start causing combativeness. For me if I want the conversation to feel level between two equals I'll instead fill the pauses with word-salad appropriate to whatever the context is with a couple of words in there to ping reactions. 'Oh wow, yeah the more I think about this the more I'm just... wow. Yeah that's annoying', where 'the more I think' is reflecting back that I agree there's something to what they are saying and 'annoying' to cause them to reflect on the irritation, trying to draw out that feeling more so they can then talk about the next layer down, but it's still basically a pause, it quietly says 'I hear you, I don't have anything to say right now, so go on...'

That's your winning hand right there. "Yeah I hear you, but I'm deciding as the lead to do X". Shit sandwich style you can wrap it with "I love this! Keep these coming! I need to know perspectives and ideas, no bad ideas remember, keep them ALL coming! I promise as long as we're not too toasty with too much going on, I'll listen and I'll keep doing that as long as you're happy that when I have to put my foot down, I can do that". Then the foot down statement. Then the "..but seriously, lets get a proper ticket in on this, yes I've decided what we're doing but we should still recognise the full story here so {insert annoying persons name}, write up a full ticket on your perspective here into the techdebt pile and tag me when it's done so I can cross reference it with my Architectural Choices doc."

In every way you're constantly saying "I am king here". It's not up for discussion, it's not debatable, it's not a choice it's a fact.

...finally if you need to revert to the 'At the end of the day I have to decide what I want to end up in court with, and right now I'm thinking this. Again I'm happy to hear different perspectives, but at the end of the day someone has to make these choices as the lead and today that's me."

...now if the annoying person starts to actually play the game and then starts actually feeding potentially good ideas, then great, you start getting them onside with "keep em' comin'!" and an occasional "...see this is perfect, I can't see everything, I can't know everything, I need us to be growing this picking the best choices and having you do this is excellent!".

...and if that starts happening, you might be growing a strong right-hand-man, I've seen people before that were underachieving but potentially capable pull themselves up and become awesome members of the team, truly carve out a niche for themselves. Sometimes they need a kick up the arse and sometimes they just need to recognise that they need to kick themselves up the arse :)