|That is a fundamental property of the Internet: You cannot rely on information being stable or remain available.
If you really need to have something documented, make a copy of that web page. It may be difficult sometimes; you may have to revert to PrntScrn - Save Page as... may not capture all you want to save. Always check the saved page.
Updating news articles is common practice with web newspapers. Sometimes, when reporting from an ongoing event, they put something along the lines of 'This story will be updated', but often they do not. Often, the 'breaking news' updates the first few paragraphs of the story, but if you read to the bottom, there can be a lot down there that they didn't remember to update - such as 'Due to the car accident, the E6 is closed for all traffic', but the (updated) headline and first few sentences declare 'E6 is now open after having being closed for two hours'.
Sometimes, when revising 'facts', they add a small note indicating that 'A previous version of this story said so-and-so. This has been updated to such-and-such'.
The one newspaper that really p me off was one where I could provoke an update. Officially, they were open to reader comments. If you made a comment that was in conflict with the newspaper's views, the article would be 'updated'. Several times I compared the article as it was at the time when I made my comment, with my comment displayed, showing that it was accepted, with the version marked 'Last updated at ...', and not a single character was changed, except for the 'Last updated' time.
And the list of comments were empty. Each update version had its own chain of comments. So they could pretend to accept disagreeing comments, while wiping unwanted comments by making a no-changes 'update'. If asked, they could present a technical explanation ('Every revision has its own comment chain - that's just how it is!'. And it was true: The new revision got a new URL, so if I saved the URL to the revision I commented on, I could use it to retrieve the version with my unwanted comment still in the comment chain.
I think it is far more honest to simply declare that 'We do not accept comments in disagreement with our views', and either inform the commenter the reason why he was rejected, or leaving an entry in the comment chain indicating that a comment was censored. Preferably both.