This proposal would:
Prevent visitors and low-rep users from quickly determining which answers are terrible.
Reduce the usefulness of downvoting bad answers (since you can't flag them).
Make it more difficult for new users to realize there is a problem with their posts.
Send a message to new users that they need to be shielded from the community.
Give them a heart attack when they finally get enough rep and see the downvotes.
And what would this all be in exchange for?
- Making users with bad posts think that their posts are good so as not to be offended.
This would largely defeat the point of downvotes on particularly bad questions. Remember, votes aren't just for users to feel good about their own posts or realize their answer is not ideal. Votes are supposed to tell people who don't even have an account about the quality of a question or answer. Imagine someone searching security-related information online and stumbling across a Stack Exchange site. One answer, explaining the solution, is +1 while the other, giving dangerous advise which can result in a security breach, is -4. The person stumbling on this would not immediately realize that one of the answers is very, very wrong. They would think it is fine!
If users unfamiliar with a particular subject are unable to tell the difference between a new or neutral answer from a heavily-downvoted answer, the advice to downvote bad or dangerous answers rather than flagging them for deletion (after all, flags should not be used to point out inaccuracies) is pointless for everyone but the regular users. Before I registered, I can't tell you how many times I've seen an answer and known that it was wrong because it was downvoted.
The voting system is bad enough as it is (low-rep users and visitors will think that a highly-controversial +9/-7 answer merely got 2 upvotes). Making it more difficult for such users to quickly tell if an answer is incorrect would make the site less useful for new users.
What do we really need to do? We need to make downvotes less personal. Create a notice explaining what a downvote is and linking to various help resources, explaining how to improve their post and why it may have been downvoted. We already have rep capped so it cannot go negative, since overall rep is not as important to the community for determining the quality of a given answer. This allows new users who do not understand the site to recover from a few bad initial answers.
Perhaps an alternative solution, if new users, despite being adults, need to be handled with kid gloves, would be to cap visible downvotes at -1 (perhaps shown as < 0). This would be visible only to the owner of the post. Everyone else (including other low-rep users and guests) would be able to see the full vote. A link to the FAQ could be shown to the owner of the post.
I do not ever want to have to leave a comment on a -8 answer along the lines of:
I know you can't see it yet and think no one voted, but your answer actually has 8 downvotes. You might want to improve your answer (and soon, because most people do not retract their downvotes!) before you risk getting suspended.