Reddit changed the policy last year, officially they still tolerate alt-accounts but most subs ban or restrict showing your content unless manually approved by mods.

I handle it so that alt-accounts under specific karma level and account age are hidden and I approve posts manually. In bigger subs they just never review comments, so the chance that your comments are hidden increase. If you then continue posting things you might trigger the bot to flag your account.

Image

This reduces 90 percent of clowns. I think most subreddits use automoderator to do that.