..., why should he join Twitter in 2018 instead of being active again here?
@satoshi twitter account was registered in 2007 . It was inactive from 2009 until 2018 .
https://web.archive.org/web/20230000000000*/https://twitter.com/satoshi .
I have to say though that there's no proof that satoshi nakamoto registered that account as tweets were protected .
The link doesn't work so I can't open and check it, anyway someone could have simply bought that username, it wouldn't be the first time and for sure it won't be the last one. Also let's not forget that Satoshi always kept a low profile: he manly used this forum and emails to communicate, he never used any kind of social media like Facebook, that already existed at that time. I really can't imagine him using Twitter now, after all these years.