Sorry to post this here, I couldn't find "JetBrains General" section. I first registered in YouTrack to report a bug. Then I had a question about TeamCity documentation and was expecting to leave a comment, but had to register another account in Confluence, and it's waiting for admin validation now. Then I decided to go and ask on forum, but had to register yet another account in Clearspace (devnet.jetbrains.net). What's interesting is that I can now login into YouTrack with this Clearspace username, and YouTrack profile shows username from the first registration. But it doesn't work vice versa, i.e. I cannot login with YouTrack-only account into Clearspace.
This is quite confusing. Any plans for single-login system across Clearspace, YouTrack and Confluence?