To be honest from my understanding Fedora 14 had almost 100% support for that Thinkpad. I do believe that the issue was no sound card support. However, since it has been roughly a year since Fedora 14 was released they may have corrected the Sound Card issue with the release of Fedora 15... now Don't Quote me on that.
As for "Support" the Linux Community is for the most part "Open Source" and I will point out that yes there are a small number of manufacturers that have started building drivers for Linux,again this is a small number.
Now for the HCL. To best use the HCL or to get a better answer for Supported Hardware it's best to look at each individual piece of hardware. So with that said we will use my HP-G60 as an example when asking about Hardware support....
To answer your question in regards to posting in the Fedora Forum. That might help to answer the specific question about complete (100% hardware support) and possibly provide any work around needed.
I did find a couple of posts using Google running this search term:ThinkPad x120e fedora -- That show that Fedora 15 runs fine on that Thinkpad, but you may want to use either KDE, LXDE, or XFCE. I personally prefer KDE and do not really care for GNOME3.
Here is a forum post for the Thinkpads, that might help you out: