Followup to bug #644169 (comment 155). Siddharth noted that the tabs in Thunderbird looks slightly different from those in Firefox.
Created attachment 583183 [details] thunderbird and firefox tabs side by side This is a screenshot of Thunderbird (with tabs on top applied) and latest Firefox Nightly. Little difference between them as far as I can see.
Maybe the colors look a bit different? It's hard for me to tell. We could do away with the boldfacing for the active tab though. I'm not sure that's really useful anyway.
Boldface is was fixed in bug #713071 Closing this with WORKSFORME Feel free to reopen if anyone disagree