I applied what was requested on https://bugzilla.wikimedia.org/show_bug.cgi?id=13214 having read (as far as I could) the discussions taken place previously about this feature (and the vice versa). My general understanding was that the opposite (forcing a scale up) was somehow turned down previously, although it has been practiced lately.
I had my own reasonings in support of stopping images less than 120*120 to scale up. Duesentrieb materialized my idea in few words excellently while we were chatting over IRC: "scaling up generally doesn't make sense. maybe it would be nice to be able to force it in some cases, not sure. if that should be allowed, it might be best to leave it to the client". If you ever use a slow internet connection and browse one of the galleries of small icons on Commons, you will notice how page load is extended merely because the images are being downloaded in a larger (in KB) scaled-up (thus no more nice looking) sizes.
However, I'm sending this email, not to insist on my reasoning, but to say that I didn't apply that change because of my own desire, but I did it because I thought there has been a (shadow) agreement about this.
Certainly, I'm open to comments and suggestions. Maybe we can reach a final solution which satisfies both sides this time.
Cheers,
Hojjat (aka Huji)