[xiphias]

That's the worst thing to do: doesn't provide any value at the part that matters. It may worth to improve code quality where it matters (the business logic), but to improve it where it doesn't matter is a waste of time to both the employee and the employer

[reitanqild]

I would think this was implied:

Only noobs like myself years ago would go ahead and refactor a lot of code during work hours without a good reason.

However when you stumble through something and finally understand the idea behind it (good or bad) then it might be a good time to add a couple of tests.

And when you have a few tests that covers nearby code you can hopefully find the courage to make a few surgical cuts to remove the worst tumors. ;-)