This one may be unnecessary and/or unpopular but it's one of those little things.. it could be scripted but I've had issues where even the mentions were adding a suffix and other small issues.
It would be very helpful and a very nice feature to have as an option on an IRC client.

Thanks.

Khaled, just a reminder before the new release, have you considered this? Sometimes I think people ask so much you get overwhelmed with features to check and add.
Thank you.

Thank you for adding this feature. I have to ask one extra thing, would it be possible to make it register the space too ": " instead of just ":"?

I didn't understood...

How does this works?

Supporting this would require a significant rewrite of the tab completion feature which currently parses words based on spaces and cursor location.

It would also require changes to how tab completion works, since it currently only tab completes if the cursor is on a word and not on a space. A suffix with a space at the end would result in the cursor being placed on a space, preventing any further tab cycling.

For now, this feature will not support spaces in suffixes but I am going to add this to my to-do list.