What a good question - this is less of an answer, and more of some possible answers, for others to think about. I would agree that changing the layout of the page because the language causes size problems is a bad solution - surely there must be some form of abbreviation in the German, which could fit into an enlarged button. There should be consistency about the style and layout of sites.
The challenges are languages where they don't read from left to right. I don't know if any studies have been done on whether Arabic or Hebrew readers scan the pages differently, but I am sure some of the positioning norms might differ, if people start on the right. However, I think I remember reading that even for these languages, menus on the left are appropriate - I think this is to do with the fact they are accessed by the mouse, at least initially.
Chinese and Japanese may also differ in their page scanning, and many of the same issue will probably apply. There are more issues that are raised by these cultures about colours - once again, I am not an expert, but the norm of Red, Amber, Green - even the Red as negative and the Green as positive - are not universal. While they can be learned, identifying the appropriate colour schemes, and the meanings of colours, can be important.
A related matter is that mourning or wedding colours are not universal. So, for example, a site that has a strongly purple theme, may be seen perfectly OK in the West, but in countries where Purple is the mourning colour, this will be seen like a predominantly Black site would be seen in the west.
I also know - from those HSBC adverts - that numbers are sometimes culturally significant. So taking people through various steps may hit lucky or unlucky numbers. The fact that 13 is unlucky in the west means thsi is often not reached, but this indicates that many lower numbers have significance in China. So having 4 steps may not be considered auspicious.
As a general rule, I think it is important to know the culture that the UI is being developed for, and the way that the features may be interpreted. It is about applying the same rules that we apply to anythign else in UI, but coming from a different cultural perspective. It means understanding what rules are cultural, and re-interpreting them.
Which is sort of what you are asking. But I hope this might have opened up the meaning a little.