https://forum-en.guildwars2.com/forum/game (requires beta account)
Devs and Community managers are very active, so there is good chance they read your feedback.Forum Closed to Posts 9:00 AM PDT Wednesday, May 2
The ArenaNet team would like to thank you for posting feedback about the first Guild Wars 2 Beta Weekend Event. Your feedback will help us improve the game. Thank you!
The forums will be closed for posting, starting tomorrow, May 2 at 9:00 AM PDT (to see this time in your time zone, please visit this link). This will allow our teams to read and sift through all of your feedback.
The forums will remain in read-only mode for a few weeks.
If you want to just thank them for beta weekend I suggest this thread https://forum-en.guildwars2.com/foru.../Thanks/page/1