This question was recently in the review queue awaiting edit approval. The edit was made by a script that repairs broken images & replaces off site images with local copies. In this case the image shows some matrix math which can now be illustrated with MathJax.
As such, I'm not really sure what the proper course of action is - here's what I considered:
- Approve the edit
- It's an improvement since prevents bit rot. MathJax can be added later.
- Improve the edit
- The basic idea is sound, but it's not the best way to do it. Avoid disincentivising the work of others, while making further improvements.
- Reject & replace the edit
- The question does need an edit, but it requires an altogether different course of action. Reject the script's edit & replace it with MathJax.
This particular case might not come up frequently, so it might be better to generalize a bit further: what's the course of action when an edit is useful, but doesn't represent the best possible course of action?