That user was me – I'm one of ten community moderators for Super User. We're basically the people who take care of handling flags and keeping the site clean. We also try and give guidance to new users regarding certain aspects of the site they may not be familiar with yet.
In that case, it's editing. There are a few key points about what to do when editing:
- Fix any spelling or grammar errors. Be thorough.
- Fix or add formatting
- Remove excess such as "Thanks", any greetings or signatures, "Hope this helps", etc.
- Do not change the meaning of the post – always respect the original author
- Generally, always try to improve the post. If your edit doesn't make the post better, then better leave it to others.
You can also edit a post to include additional information or fix obvious errors. In that case, try not to change too much though.
When reviewing questions and answers should one remove text that one know for a fact is wrong or should one tell the poster in a comment and tell the person to rewrite the text?
If you see an answer that makes a wrong statement, you can of course try and correct it. There's no specific rule there: if it's easy enough to fix the post, just go ahead and do it. For example, if there was a command with a syntax error, or any other minor thing.
If however you'd need to rewrite the whole answer to make it correct, and it contains too many incorrect assumptions, then refrain from editing it. That'd be a too radical change and would change the original meaning and intentions. In such cases it's better to downvote the post and leave a constructive comment explaining what's wrong and how the poster could fix it. Once they edited their post you can remove your downvote and turn it into an upvote.
In the specific case of your example, I'd like to stress the fact that there was no wrong statement to begin with though – internal IP addresses probably start with 192. Removing that part – which would actually help users who aren't that familiar with networking – wouldn't improve the post in any way.
If you have any questions about specific edits you want to make, don't hesitate to ask regulars in Super User Chat.