Typos annoy me to no end, so I feel your pain. Hope I'm not out of bounds here, but you can edit the ost_ticket_thread table. Look for the ticket ID, and find the line that corresponds to the internal note you'd like to edit. Make the change, save, then go back to your osTicket instance and see the change has been made, and the typo is nowhere to be found.
If anyone does this, and if you use osTicket to document any kind of legal compliance, then you better have a good set of controls on who edits the data in this way, and what edits are made (edit history). Otherwise, it will invalidate whatever controls you have that are based on the data in osTicket.I would hate to fail a compliance audit because someone thought correcting a typo was that important.Jack