From the second link:
> FLP and the Two Generals Problem are not design complexities, they are impossibility results.
Two generals, in its impossible form, isn't applicable here. For example, this proof[0] depends on the deterministic form being impossible to solve in a finite number of messages. But why would we care about doing it in a finite number of messages? By that measure, at-least-once delivery is impossible too, yet neither you nor the blogger seem to have a problem with that. The solution is easy and common: send a message, ack new messages, retry if you don't receive an ack, never ack an ack, and always ack a dupe. As long as you aren't disconnected forever, this will give you at least once delivery.
FLP only applies in the case of faulty processes. Specifically, FLP arises because the faulty process must either (1) ack the message before handling it, or (2) handle it before acking it. (1) fails if it crashes after acking before handling, causing it to forget it ever received the message (at-most-once). (2) fails if it handles the message, but doesn't persist that fact to disk, so that when the dupe is received it doesn't know it already handled it (at-least-once).
Urbit processes events transactionally (like a database), so you're guaranteed that if you received an ack it's because the other person has persisted that message or its results, and it won't forget about (i.e. they've persisted any state changes related to it). No faulty process, no problem. FLP impossibily doesn't apply.
I suggest actually learning about proposed solutions to problems rather than recalling that someone convinced you they were impossible to solve. Proofs are powerful because they're incontrovertibly true, but they only apply if their conditions are met.
[0] https://en.wikipedia.org/wiki/Two_Generals%27_Problem#Proof