1.
you are setting those two variables u+m and u+g, but apparently you can use their value directly, without using a variable.
So, it would be this way (not tested!)
{.for each|u|{.replace|;|{.no pipe||.}|{.get|accounts.}.}|{:
{.if
| {.and
| {.administrator={.get account|{.^u.}|member of.}.}
| {.not|{.get account|{.^u.}|is group.}.}
/and.}
| {.^u.} - admin<br />
/if.}
:}.}
2.
there's no command to delete accounts, currently.
Would you need it?