As my German grammar demands that I separate an extended introductory subject phrase with a comma, I feel a strong impulse to put a comma in such a sentence as the one on the page before - but this would be wrong, because subject and verb must not be separated. This holds also true for clauses substituting the subject as in the examples below. What can we do to avoid this problem? Simply determine the finite verb and then recognize what belongs to the subject. I have underlined the finite verbs for you here.

The question whether we should keep and finally kill animals for food has…
What is striking is that …

The same is true for fixed expressions. Fixed expressions are not separated by a comma in English as they are in German. When one (usually the second) piece of information serves to define what is meant by another part of the sentence, we mustn’t put a comma.

The problem does not arise with comparisons.
Diese Sektionen sind gewöhnlich kleiner als die Fleisch, Geflügel- und Fischtheken. (Vergleich)
Usually these sections are smaller than the meat, poultry and fish section. (comparison)
 
But be careful with fixed expressions ...
Das liegt an der Tatsache, dass es in jeder Mensa eine vegetarische Theke gibt.
That is due to the fact that there is a vegetarian food counter in most university cafeterias in Germany.

... or consecutive clauses ...
Das bedeutet nicht, dass wir nicht auch Salat essen können.
That does not mean that we could not also eat salad.

... or dependent infinitive phrases.
Der Gedanke, Tiere zu töten und ihr Fleisch zu essen, liegt ihm fern.
The thought of killing animals and eating their meat never crossed his mind.