In the very off chance that its not the same HD wallet, I just don't understand why "different users" would entrust each other with their private keys unless they were very close, or more likely, the same person.
I've been entrusted with private keys on multiple occasions. I can also imagine someone uses someone else's addy to join a certain campaign, for instance because he owes him money, or because he's not interested in weird "tokens".
It's all possible, just not very likely.
including each other in trust lists is quite bad.
I can even understand wanting to see feedback left by your alt account by default, but it's for sure abuse of
DT1 voting power
using sockpuppets and deserves to be
blacklisted from voting if they're owned by the same person:
Note that those 3 users all have
more than enough votes to reach DT1 with or without votes from vycl87 and koincik.
I read up on how Wallet Explorer works (it's a lot simpler than I thought) and I have to retract my use of the word "indeed" -- its just by far the most probable outcome.
I think you've missed my point: how do you know the wallet is HD?
Related:
My assumption was the addresses were random.
No. Pseudorandom at best. Read about derivation paths in HD wallets in detail. You can use the xpub to deterministically derive the children. HD stands for hierarchical deterministic for a reason.
I know about xpub (but never memorized the exact details): as far as I know, it's not possible to know addresses are derived from the same xpub unless you know xpub, right?