Hey, sorry, you may have misunderstood me -- I'm not saying that it's only Moxie who's considering Telegram insecure. I meant that Telegram is considered insecure by many experts; but when it comes to the security of Whatsapp we can only rely on the claims of Moxie and Facebook, without the chance for open review.
> With a closed client that allegedly implements a secure encryption method (we also know it's good because it's open as well) there's a chance it doesn't work the way it's supposed to work, but there's also the chance it's working as intended.
However, from the other side: Telegram is not _trivially_ breakable (there's a 2^64 attack, which is not 'trivial'), but Whatsapp might very well be simply MITM-ed by Facebook. So you could also look at this from a different perspective and say "A powerful adversary could probably break Telegram messages, but maybe all Whatsapp messages are immediately decodeable by Facebook".
Also note: you have provided 5 links, but [0] simply refers to [1] and [2], [1] says that "We stress that this is a theoretical attack on the definition of security and we do not see any way of turning the attack into a full plaintext-recovery attack", [2] claims that there could be attacks (but does not provide one), [3] is a real attack, [4] is not about an attack.
So while I see that there are valid concerns re. Telegram's security, the links you have provided are a nice example of the Internet echo chamber.