This is definitely possible but this setup would have to be a customization procedure per site. Adding this within the 'default' XOOPS installation would defeat the purpose of a modular implementation of features as you have 1 module dependent on another. Some XOOPS site will not have forums, some will use other forum mods like phpBB or IPB.
The comments system is part of the core (I think) and it allows other modules to have a comment system even without newbb.
But, honestly, I think this is a really nice feature to have.
If the IP gif doesn't work (it should, but...) you can just use the Smarty tag for the IP and place it somewhere inside the post area, similar to the Comment posts.
Take note of the Smarty conditional tags, though, so that it can only be viewed by admin.
This may or may not help, but the same error happens to me when I use the MySQL Control Center program to access my DB, and then try to login to my XOOPS site. This is for my local setup. I just turn off the connection from the program.
Were you using some 3rd party program to access the DB simultaneously with browsing the site? I don't expect that to be a common problem, but it does happen to me.
Go to System Admin -> Mail Users. Choose "Send message to inactive users only (optional)".
In the body, use the {X_UACTLINK} tag to put the activation link. Add some more text/tags as you want. Check the left column of the body field for more useful tags.