How many non-technical readers are a) going to see that HN post, and b) have any idea what the gobbledygook in those first few posts means?
Yahoo is definitely handling this badly: they should have offered an export tool, given a longer window, and been clearer in their messaging. But the claim that they didn't notify people (and just put the information up in a place no one would see) is wrong.
I'll add that some group owners/moderators have not even been able to log into their groups. Yahoo was doing something with needing a yahoo email to get in as admin, even when a non-yahoo email was associated with the account. Those people that lost access to their yahoo email account have been totally SOL.