It's a very nice forum setup for a small community, very easy to see new posts and so on. But still, plenty of people probably don't look at it. Maybe an email sent through the site's messaging system? Default settings send them a normal email notifying them when that happens. I think many people will miss an email to their normal account, when they already receive so many from this site in the form of notifications. And those who look closely enough at their emails to see it will still receive a notification email.
Also, a translator link could be included in your message.