Earlier quoted context omitted.
Please tell me more about YC's business model.
HN is mainly goodwill for YC (any VC would pay a fortune to have HN and its audience). So the parent comment seems to suggest that it's damaging to the goodwill of the site to disable signups. If this was a permanent change, I'd agree, but it may be temporary, and it's not totally disabled (you can still signup by submitting content, as someone else wrote).
* At least, this was all true last I heard. I have not looked at their application or application rules/process recently.