User registration spam on blog hosted by WordPress.

Hi.

I’m having a big issue with a blog hosted on WordPress.com. I’m experiencing a lot of user registrations, which are sent to me by mail. They’re clearly spam.

I’ve found tons of people advising other people to use plugins to avoid that.

That’s good, it works for my self-hosted blogs, except that it appears that plugins are disabled on WordPress.com. There’s Akismet, who’s doing a great job dealing with spam, I guess, but I found now way to avoid that spam.

And I have to admit those emails are getting on my nerves.

Is there, by chance, any way to avoid this?
Thanks in advance,

Karl.

P.-S. — I’m truly sorry if that question has already been answered. I’ve done my research, but was overflown by answers working on self-hosted blogs and plugins.

P.P.-S. — Moving the blog to a self-hosted place isn’t a solution I can consider.