I was surprised to discover that @tchrist and others had declared this question about language usage off-topic. The "off-topic" flag description says:
This question does not appear to be about English language and usage within the scope defined in the help center.
The Help Center specifically includes questions about grammar and discusses nothing about excluding questions about usage. The fact that there's actually a tag ("conversational-deletion") that describes the question strongly suggests the question itself was on-topic.
I honestly don't understand why the question was declared off-topic. I was especially disappointed when @tchrist declared that:
Of course it's "grammatical", since "grammatical" is defined to be "sounds ok to native speakers". This is what we call conversational-deletion.
First of all, by declaring the example "grammatical" (right or wrong), @tchrist has admitted the question is valid and should not have been put on hold for being "off-topic."
Second, I'm familiar with what "conversational deletion" is, but was disappointed to find the tag has no meta information. I agree that "sounds OK to English speakers" is basically the underlying concept behind the acceptability of conversational deletion, but I'm pretty sure every English teacher in America would disagree with the claim, "'grammatical' is defined to be 'sounds OK to native speakers.'" That assertion is tantamount to, "there are no rules, this site has no reason to exist."
Therefore, I'm hoping to better understand the rationale behind putting the question on hold. I'm also hoping to understand how a blank tag justifies downvoting all the answers and, apparently, the question (which appears to be what happened, though I may be wrong about this). The action appears draconian to me, and I'd like to understand why it was deemed acceptable.