Airbnb has made permanent its pandemic-era prohibition of parties at the properties rented out globally through its app, saying Tuesday the rules have been effective against problematic events. The rental platform has gradually tightened its policies on parties after complaints and some high-profile trouble, including a 2019 shooting that killed five in California. Airbnb provisionally barred events in 2020 as a measure against the spread of Covid, but it turned out to also be effective against large or disruptive gatherings. “Over time, the party ban became much more than a public health meas…