Future packages and upstream updates to existing packages that depend on ucommon now require ucommon 2.1.3 or later, which also introduces a new abi (libucommon3). There are a number of bug fixes related to this, and the addition of unicode support. ucommon 2.1.x/abi 3 is only intended to be introduced for Maverick and later going forward, and not for earlier releases. ucommon 2.1.3 is also fully backward compatible in the sense that dependent packages built against older releases of ucommon can use the new ucommon release if thy are rebuilt, however this may not be guaranteed in the future, and this is why I do not suggest updating lucid or earlier with this or future upstream releases. If security fixes or other changes are needed for lucid (or earlier), they will likely be done using further 2.0.x releases or patches for the existing 2.0.x package in lucid.
I am going to upload a debdiff and related files for updating Maverick shortly. I need this in because this will block other uploads for I have Maverick, but there is no urgent issue otherwise.
primary package diff for 2.1.3