When shareable Knowledge Base links are shared with customers who need to log in to view the Knowledge Base, a really unpleasant error message appears ("Something bad happened"). You can work around this by forming the URL as follows:

https://<instance>.atlassian.net/servicedesk/customer/portal/portalID/user/login?destination=portal/portalID/article/pageID

It would be extremely helpful if shareable links were formatted like this by default.

It would also be nice if this URL were customizable.