Add a see also section on each issue, which lets you add other issues which are related. These might be dependencies, duplicates or just tangentially related ones - there are often varied reasons for referring to other issues so good just to have a loose link between them.
A way of inviting users to participate before a project is launched, and keeping them on a list(s) so that you can let them know when your project launches.This could also be used as a way to promote growth later via user referral schemes, with a little modification.
Allow hosting a project website at project page. You can host your entire website at project page if you wish, or just certain components of it, like your community, your public roadmap, or your status page.
Community is really important to finding the customers you need, and to nurturing your relationship with customers. From product ideas to bug reports, a public community helps you build trust with your users and communicate clearly with them.