This a general reply, i'm just replying to Slade because his is the post I was reading before making this reply
It might be a good idea to add a check to make sure they don't try and make you join 0 (/join 0, /join 00, /join 000, etc), which is the equivalent of /partall.
on *:text:!join *:#:{
var %a, %b = $regsub($$2,/(?<=^|\x2C)0+(?=\x2C|$)/g,,%a)
join %a
}