It's not only the 15 that is experiencing this problem. MY XPS 13 9350 has a swollen battery after just 16 months use from new causing casing, touchpad and keypad displacement identical to that shown in pictures of affected XPS 15 models.
Contacting Dell support was a complete waste of time. They dismissed that there was a problem completely at first, but then admitted that the 9550 model did have a problem with swollen batteries. As far as Dell are concerned it's out of warranty and furthermore they cannot help directly as there is no Dell service centre in Cyprus, where I live. I have found many XPS 13 owners reporting the same problem even on the Dell forum, so to deny the XPS 13 also has a problem is farcical. Perhaps not to the same extent as the 15, but the problem DOES exist. It's time that Dell had the integrity to admit that their sub standard batteries will swell and eventually cause damage well before the battery life is up.
The good news is that today I removed my Dell battery before serious damage occurred, and the casing and keyboard returned to the correct shape. The space bar now works again as it should. The three left hand cells were all swollen both sides. But why has the battery deformed so early in its life? In my view, it should never do this. Finally, with Dell's head in the sand attitude, is the XPS 13 / 15 one day going to be another Note 7?