Then you want versioning. Please don’t just dismiss not recommending it as “frowned upon”. It’s just that there are much better solutions to the problem you have than “ignore deletes”. Your initial statement about “accidentally deleted stuff” is a prime example of why one uses Syncthing’s versioning and periodic backups.
Edit:
What about invoking the wrath of the internet by installing a word-filter that throws all posts mentioning the option who’s name one doesn’t write into the moderation queue? (in case it isn’t clear to anyone: I am kidding - but really, don’t recommend it).