What this command sed "/[\t][:0123456789]*$/d" means?
izzit add commas to numeric strings, changing "1234567" to "1,234,567" ?

one simple idea to get a abstract idea about the sed script or command doing
see the command
sed "/[\t][:0123456789]*$/d"

here d is the command and thus it does some delete operation
and since there is no s command it can be sure that it does not do a pattern substitution

here the pattern is
/[\t][:0123456789]*$/

and it says the pattern contains tab then may be : or any digit then anything and then end

please try to give examples to prove what u feel or demand to be true

Rakesh UV