New ideas about how to make SVG files smaller are always welcome. No need to implement them, though. Just create an issue on GitHub that explains your idea(s).
If you found that svgcleaner broke your image, firstly open them (original and cleaned) in Google Chrome, since it has very good support of the SVG spec, unlike many other applications.
- If images still render differently - then they are probably broken. Create an issue on GitHub with your image attached to it.
- If images are rendered the same - then there are some problems with your rendering application/editor. Such cases are not treated as errors, but you still can open an issue.
Note that actual cleaning takes less than 30% of the execution time. The other 70% is spent on parsing and saving. So, if you're investigating performance issues, you should start there.
- English grammar fixes are extremely welcome.