Priority

Slack -> xxx:

✔︎ ~~😃 -> actual smiley~~
✔︎ ~~@username is displayed as <@U...>~~
✔︎ ~~#channel is displayed as <#U...>~~
✔︎ ~~unescape HTML ? (for XMPP/Telegram at least)~~
✔︎ ~~/giphy, /gif, link expansion~~
username has to be user@slack-service?

Slack -> XMPP:

✔︎ ~~username passed as username to XMPP~~
http://git.emojione.com/demos/ascii-smileys.html
markdown to xmpp xhtml
✔︎ convert \n to <br> for XMPP XHTML messages
"Set channel purpose" -> Set topic

xxx -> Slack

commands (text beginning with /) should be sent as commands (careful about /o\ and /me etc.)
set topic -> set channel purpose

xxx -> XMPP

Per=user login with different resources

xxx, xxx -> xxx

Log all errors

Extremely low priority

xxx -> IRC -> xxx:

implement IRC support (req. by Mendor)

xxx -> Telegram:

html escape/unescape
do something about links http://dmitriid.com/i/gc4ukqjsgw4u1qb3.png

Telegram -> xxx

stickers
user should be user@telegram or similar