Not sure if or where the limit is for truncating a URL link in a post.

During a post preview when adding the color command the full link is truncated
Code
[url=http://support.microsoft.com/kb/318380][color:#009900]Description of Microsoft Internet Information Services (IIS) 5.0 and 6.0 status codes[/color][/url]
[Linked Image from kixhelp.com]

During a post preview when adding the color command the hover shows the parentheses as missing and also shows the color codes
[Linked Image from kixhelp.com]


During a post preview with no color command the full link is not truncated
Code
[url=http://support.microsoft.com/kb/318380]Description of Microsoft Internet Information Services (IIS) 5.0 and 6.0 status codes[/url]
[Linked Image from kixhelp.com]


As it turns out though if you add enough text to the URL link then with or without color it will truncate and the hover at least in preview will show stuff it should not show.