That's right - in general nothing* is ever lost on a wiki - but don't just go reverting pages just because your point of view differs from the current page (otherwise known as an "edit war").
Start a discussion ("discussion" tab at the top, next to "page") and get it resolved, if possible, with an agreed version that most contributors are happy with. There are many opinions about many subjects that the wiki touches on - over the long term we need to arrive at versions that are broadly agreed, yet still detailed and informative.
*conditions apply.
