[c3o]

This would indeed seem to be a copyright infringement in many EU member states. For example, in Germany it wouldn't fall under the quotation exception (no such thing as vague "fair use" here), since you aren't critically engaging with or commenting on the quote, which would be allowed – you just reproduced it.

The movie studio could now hold HN liable.

Well, except that HN is not under EU jurisdiction, so it could probably choose to ignore EU court decisions against it. Bigger platforms of course won't have that luxury, so they'd need to come up with some way of limiting or avoiding that liability... or maybe just blocking EU users.

[toyg]

> you aren't critically engaging with or commenting on the quote

He's using the quote to make an unrelated point. This wouldn't be considered copyright infringement anywhere you have an impartial judiciary.

[phissk]

Your post, right here, discussing quote, makes this fair use.

[c3o]

True, I guess you could see "the comment thread" as the larger (collaborative) intellectual work within which the movie was quoted for illustrative purposes.