[cookiecaper]

Independent of social context, this type of act is generally viewed favorably. Machiavelli claims that "nothing makes a Prince so well thought of as to undertake great enterprises and give striking proofs of his capacity." [0]

How this would go down in your particular workplace all depends on the surrounding political and social context. It could either be interpreted as "Wow, that guy is such an amazing programmer that he was able to refactor our whole legacy system in his spare time! We should definitely keep him on board and learn from this kind of work, even if we can't do a full-scale replacement." or "Wow, that guy is so self-absorbed and unwilling to cooperate with his teammates that he went home in a fit of anger and thought he could replace 10 years of work in a few weekends! What an abrasive blowhard. Let's fire him next time he gives us an excuse."

The halo effect is going to be the primary determinant here. [1] If your colleagues and superiors are predisposed to interpret your actions favorably, they'll probably do so until you give them a reason not to, and vice-versa. It takes a lot of work to maintain a good halo, and it should be considered your primary job duty if you wish to have a fulfilling career as an employee.

Humans are social animals and will evaluate everything about you, including your technical competence, by the social signals you output. Successfully managing these can get complicated in the workplace due to the competing interests of the people you come into contact with during the course of your employment.

[0] https://en.wikisource.org/wiki/The_Prince_%28Hill_Thomson%29...

[1] https://en.wikipedia.org/wiki/Halo_effect