Stock attribute, so you aren't "allowed" to amend it....
The reason it is bigger on the database than in Clarity is to cope with multi-byte characters sets (i.e. non-English language) - you can see other stock attributes are the same (like the project.description).
Supported method is therefore to create your own custom status comment field and replace the stock one with the custom one everywhere. Thats clearly a pain though.... if you go down the un-supported route (hacking the meta-model in the Clarity schema) that might work, but will be an upgrade problem (at best) and possibly require lots of further 'hacking' to get the app consistent. :sad:
So no good answer here for you I think?