Do /comment <id> <comment> to add a comment to a ticket
Do /mods to see what mods are online (vanished players will not appear on this list)
Do /modhelp to get the Help page
For the normal player
To file a ticket you can do /modreq <message>
To check the status of your latest 5 tickets do /status
To check the info of 1 of your tickets to /status <id>
For mods
To get a list of all open tickets do /check <page>
You can also check claimed, closed and pending tickets by doing /check <closed / pending / claimed> <page>
To check out a certain modreq you can either do /check id <id> or /ticket <id>
To claim a modreq do /claim <id>
To teleport to a modreq do /tp-id <id>
To close a modreq do /done <id> <message
To re-open a modreq do /re-open <id> <message>
To set a ticket to pending do /ticket setpending <id>
Note that only people with the modreq.claim.pending permission can claim pending tickets, as well as see them in the normal /check list. They can still see the ticket using /check pending and /check id. That will be patched in the next update (2.5)