Ah, I think I see what you’re saying. The way that things are currently set up now is that the code isn’t checked per-se, instead it’s executed before being saved to the database, so that if it produces an error and crashes the site, then the faulty code will never be saved.
I haven’t made any change to the behaviour you describe, where pressing the back button returns you to the version of the snippet you were last editing. This functionality wasn’t really controlled by the plugin, but was something that was more a function of whatever browser is being used. In fact, that’s the way that it still works for me.
I suppose that if you did want the code to save no matter what, I could change the behaviour so instead of leaving the site untouched when a snippet produces an error, the code is first saved to the database and the snippet deactivated, then the code is run, then if there were no issues the snippet is reactivated. The problem I see with this is that if the snippet was a pretty essential one for the site, then deactivating in case of an error might not be nearly as good as simply leaving the previous version as-is.