@Nigel yes that is a fair concern. At the end of the day I expect the feedback users post here to avoid veering into defamation territory, if you had a bad experience buying something, I think it is fine to describe your experience making clear that it is your own perspective.
For example, there is a world of difference between "I paid for X and although the seller claims they sent it, I never received it" and "I paid for X and the seller never sent it and is lying to me about it!"
It's only been an issue once or twice and generally I will ask the poster to reframe their comment to avoid making any speculative claims. I'm not spineless, I will defend your right to share your experiences to the greatest extent possible, but if I find Oz Volvo is in a legal grey area with respect to defamation, I will always err on the side of caution and remove the offending comments.