Most people never notice. The ones who do get an explanation of what happened when they ask about it in modmail.

It can be rough on a brand-new account that wanted to jump into a discussion right away, but at the same time the quantity of spam hitting your subreddit once you pass the 100k mark is just ludicrous, and this is by far the most effective way to stop it.

In terms of community building, that might not be the worst thing in the world, especially if the community objective is quality over quantity.