You now can! Just type
/poll delete for help in Slack.
/poll delete latest will delete the last poll you created.
/poll delete will list your polls with IDs so you can delete a specific one using
/poll delete <id>.
At the moment there is no way to do this. I am currently working on an advanced poll with options!
Yes - if that language can be written in UTF-8 then it should just work (let me know if you find anything funny going on!)
Get in touch, I'm happy to take feature requests and feedback. The best way is to get me on twitter @florx