It would be great if when I @mention someone in an internal comment in UserVoice, they get notified via Slack. It would also be beneficial for when I assign them as the Assignee (custom field), if they were notified in Slack.

I think since the old webhooks method supported it, it should be with the new method as well. I will say the nature of Slack seems to be public first, so I would bet most want it in a public channel anyway.

+1 This is hugely important for us. The old Slack web-hooks integration allowed us to utilize private channels.

Because we have focused discussion in these channels with stakeholders about decisions, we need the ability to utilize the integration in a private channel. I'm hoping this is something you guys can support!

As a work-around for now, we may keep conversation in those locked channels private and have to create a new channel for forum updates for each of the respective forums. #uservoice_forumx_updates etc.

For the time being if this is NOT supported, I'd recommend calling it out in your documentation on the feature as I'm sure others will find the same issue.