I really don't think so since you're soliciting an email server while a regex is just some code that has to be run, and they are run on a tiny string (a mail is never really long).
Also it's bothering for the user, if you need mail confirmation then do it, but otherwise it should be a RULE OF THUMB to always avoid annoying user. Thus avoid mail confirmation.
This article is actually a really bad advice. I don't know why it's upvoted so much.
I'm not completely sure that I get annoyed when a web site sends me a confirmation email. It helps me know that the site indeed knows my correct email.
Also it's bothering for the user, if you need mail confirmation then do it, but otherwise it should be a RULE OF THUMB to always avoid annoying user. Thus avoid mail confirmation.
This article is actually a really bad advice. I don't know why it's upvoted so much.