I have previously completed 5 OU courses and they are very hot on plagiarism. I thought that I had reworded some thing I had read but had not properly referenced it and I was told that it was very close to plagiarism. I would recommend copying the way that the references are written in the OU textbooks.
You need to reference it correctly to the website and the date the comments were posted-cutting and pasting without correct referencing is plagarism-and regardless you should ideally reword and reference not cut and paste
if asked to give a commentary on subjects related to your topic/learning from the group forum do you cut and paste comments from the forum or write in your own words, thanks