Thanks for all your comments. There's certainly a lot of interest behind this feature!
We would love to hear more from you on how your team shall add and maintain multiple languages on the portal. Understanding this will help us make the right thing that fits your needs perfectly.
If you would like to help out, please take 2 minutes to answer these questions - https://jsd-beta.typeform.com/to/VS5QKT.
JIRA Service Desk Team
It will be very useful to support multi language. On Customer Portal, request details in addition, field labels and descriptions could be displayed in the user's preferred language.