I don't know if all sites have this problem, but I suspect it extends beyond just Seasoned Advice.
Sometimes we seem to go through periods where we have a constant stream of invalid suggested edits from anonymous users. Sometimes it's blindingly obvious that the edits are not appropriate. For example, we had one today, where the user added the following:
Note: This is incorrect. It is protein, not fat. Use the brining technique described above to solve the problem.
...and another one yesterday, where they added this:
i save my pine apple cores in the freezer in yogurt containers...till i make a turkey, i use chucks of lime, pineapple core and onion in the cavity...pineapple peelings on top of the turkey it is called armadillo turkey is is delicious....
These edits aren't exactly vandalism, per se. They seem like honest attempts to be helpful (one even left the comment in his edit, "just wanted to help"), and sometimes they even provide useful information, but all we can really do is reject the edit, there's no way to integrate the information except to do a bunch of manual fact-checking and commenting/answering. And it's hard for me, personally, to understand how the users came around to the idea of suggesting an edit rather than just answering the question themselves, but somehow they did.
This is certainly nothing we can't handle on the site - we get hardly any suggested edits compared to Stack Overflow. However, it occurs to me that this could be a much bigger problem on high-traffic sites, and should also be fairly preventable.
I think it's great that anonymous users can suggest edits that correct spelling and grammar or even correct minor factual errors. But certain types of edits should be instantly recognizable as invalid when they come from anon, for example:
Edits which remove or replace more than around 50% of the content (almost always vandalism)
Edits which include personal pronouns such as "my", "I", etc. Anonymous users obviously cannot speak for the original author so these edits are never valid.
Edits which add a significant chunk of new content without modifying any existing content (these should most often be replies, or additional answers, similar to above)
Some of these edits, especially the last type, might be valid for Community Wiki answers.
I'm not suggesting that we actually block any suggested edit from anon or otherwise unless there's clear systematic evidence of spam or other abuse. As I said, I like this feature. But how about at least displaying some kind of warning to these folks while they're suggesting their edit, when they meet the above conditions? Something like:
Please consider posting a new answer instead of making major changes. We want your contribution, but will not accept edits that change the meaning or attempt to reply to the original post.
They're more likely to notice this warning if it appears while they are crafting their edit, although I recognize that a lot of users won't read it anyway (just like the duplicate question warning). Still, it's better than nothing, and seems easier to implement than supporting conversion to comments/answers/etc.
It's not just about reducing noise for existing contributors. If these people have useful information, we want to try to get them to contribute it in a form we can accept, instead of having them suggest edits that just waste their time and ours. This warning would be useful for both parties, and beneficial for the site/content in general.