As far as forum rules go, providing the source is enough. Even just adding double quotes without giving a source would probably be enough to avoid a ban. Contrary to popular belief, the plagiarism rule and application thereof is very lenient. It's usually fine as long as moderators can see that the user didn't intend to pass the text as their own.

Now whether starting a paragraph with "I would like to..." and ending it with copypasta with the source mentioned only somewhere in the fine print constitutes good writing style - that's a different discussion. I think that's misleading borderline on dishonest. A literal quote should be formatted as such.