Maybe it's my age and having come up via years of Usenet where inline quoting was absolutely standard, but I find inline quoting of a discussion helps me keep the flow of discussion. I find it's easier to follow than trying to retain a lengthy parent that a commenter is replying to, also at length.

If it's a long comment it's also likely some commenters are only able to address parts of it - again an inline quote clarifies.

I've never had cause to see it as a warning sign or more likely to be someone scoring points, that's going to happen sometimes with or without inline snippets.