Yes, it will happen. Yes, we're working on it. The reasons it's taking so long are: (1) the change required is not tiny; and (2) everyone working on it has many other things to do, most of which are more pressing. That doesn't make it a low priority (it's a high priority), but it means we have to do it as a background process.
As a fellow very busy programmer I can easily see where you're coming from, but surely for several years time a background task must be pushed to the highest prio tickets eventually? Even if you simply steal LWN.net's very basic comments CSS, it wouldn't take you more than a full working day, including testing on few iPhones and different-resolution Androids. A passionate community whose quality of life needs aren't…
In pure speculation, it is possible that mobile/desktop browsers correlate with the pipeline into YC's primary business. Though the business is probably clearer.