I’m not telling anyone how they should quote others. Some use italics. Others use the quote feature. It’s up to you how you want to do it.
But LH has a good point (made elsewhere in the general discussion) that using the quote feature to repeat someone else’s entire post in order to respond to one small bit of it can be frustrating.
Note that you can edit what appears in the quote box. While you, of course, shouldn’t change what someone else says when you quote, you can certainly edit out the bits, which are often quite lengthy, that you’re not responding to. Doing this makes the best of both worlds: the quote feature identifies who you are quoting and it’s concise.