Now it's status-completed.
I've declined to do anything with the vague optimization tag. Since the question was edited, it's an orphaned tag. If there's another type of optimization that comes up (i.e. energy), we can change add synonyms for the different spellings.
The reason for that is if I would've added optimisation → code-optimization and optimization → code-optimization, any time a user adds either of those tags, it will, without warning, replace the tag to code-optimization. IMHO this is a major flaw in the system. It should warn the user.
A quick note: from searches, it seems like spelling it with a
z is the most common way, but is still widely used. However, since SE is a US based company, we'll stick to US spelling. I know that Stack Exchange has users and countless countries, but it's simpler to stick to one version of English spelling, the one that's built into the engine/code base.