You're right supra, our members don't bash each other but we have had people come and bash shops and online retailers etc. So it is a concern.
What I say is, go ahead and make your post as a regular thread. As long as it is completely factual and not inflammatory there's no problem putting it out there.
Something like, "My heater exploded. I don't know if it was a defect or just a poor quality heater but I personally won't buy another one." is something acceptable. Whereas, "Fluval heaters are sucks! Mine exploded because it was crap."
Obviously those are simple examples but you get the idea.