first, why would facebook do this? Is it anything more than negligence?
Second, what are the consequences besides some facebook messages ending up truncated? Do excessive messages of this type choke up mailservers or anything else of the sort?
That's pretty much it. They already fail to provide cross-browser compatibility for their website (Opera has long had problems with it), so this is just another way of thumbing their nose at open standards.
what are the consequences besides some facebook messages ending up truncated? Do excessive messages of this type choke up mailservers or anything else of the sort?
From TFA:
as spammers make the same mistake rather often - I've seen line length checks for Quoted-Printable implemented in antispam software.
So I'm guessing quite a few emails from Facebook are getting sent to people's spam folders.
It's likely much less "thumbing their nose at open standards" as it is just a matter of making sure their software works for the vast majority of their users.
I know that's how I develop software, anyways -- if there's a quirk in a browser used by a very small percentage of users that's not entirely simple to fix, I don't. It's just a matter of priorities: create new features and upgrade existing ones for 99% of your users or fix features for 1% of users. Depending on the feature, you make a rational decision.
Moreover, I seriously doubt that a company like Facebook has any manpower issues when it comes to fixing bugs on their site.