The old login handler was replaced today with a completely new one that would seemlessly import your Steam profile to the website.
If you've already linked your existing steam accounts via the old login handler, your data should already be imported onto the new system.
If not, or if you haven't yet linked your steam accounts, follow the following instructions:
1. Go under Account Settings
2. Click under Steam Integration, then just login to your Steam account
3. Once linked, head down to your profile
4. Hit Update
5. Voila! It should be linked now and should show in your forum posts.