Thank you that was what I was looking for.
There's also the option of copy-pasting and using the 'quote' button while you're typing a reply. The quote comes out as above, without saying who you're quoting. It's useful if you want to quote several different people, but like you said, it feels a bit like plagiarism.
Also, make use of the 'preview' button before you submit, to make sure it looks roughly like you imagined it
should.