What does “#?#” do in an adblock filter?

While browsing the EasyList adblock filter list, I saw a commit which edited several filters that use :has-text() to put #?# after the website domain instead of ##.

instagram.com#?#div > article > div:has-text(Suggested post)

The uBlock Origin documentation says that ## is always present in cosmetic filters, so what does #?# indicate?