If the link is dead (as in gone for good, not just unavailable due to a network failure or server misconfiguration), the best thing to do is to find where the page has moved. In cases such as this, where the resource is just gone, you did well to remove the link.
What you didn't do well is that you only removed the link, but left the surrounding text explaining the nature of the link. You should have removed that as well. You should also have noticed that the image is broken as well and removed it, as well as the bits that belong in the author's diary but not in a Stack Exchange question.
And when you take all of this out, here's what's left — the useful part of the question:
I wrote a basic tile engine, but having never attempted this before, I am really struggling with handling sprite collision detection and implementing realistic physics for gravity.
For any other game hobby writers, can you point me towards some walkthroughs on the best way to approach this?
(Followed by a follow-up question that nobody had answered anyway.)
In this instance, there isn't anything left to the question. So you should have edited the question, then flagged is as “not a real question”.
I disagree with the assessment that the edit was a “radical change”. Removing a broken and unfixable link cannot possibly be a “radical change”, since the link was not conveying any meaning whatsoever. “Too minor”, quite possibly.