Temporarily banning shared IPs from creating new accounts when there are problems would sort of make sense, in a wrong but convenient sort of way. Permanently shadowbanning them only for chat and including existing accounts which have never misbehaved, which is what they've done, can not be so easily excused. It's been like this for years. At some level they must know by now that it was a mistake, but I imagine there's some kind of stupid office politics type of situation preventing them fixing it.