Since I answered the question with the "politeness" answer, I thought I might jump in here too.
I think it is perfectly friendly to start with just the context of your question. However, do give as much context as is possible. Starting with the context is important and logical, and is the best way to assist the people who will try to answer a question. There are not really other, more polite ways to start questions in the context of the Stack Exchange website.
This Code of Conduct from the English Language and Usage SE site might help. When you scroll through it, it gives examples of "unfriendly" phrases vs "friendly" ones.
To give you specific examples:
One thing especially good in the "Why does she have to call her roommate at work?" question is that you provided a link to the source that your question originally came from. Providing links to what caused a question helps others understand the bigger context around a question. Understanding the bigger context is useful because, when seeing that, the person answering may notice a small aspect that contributed to a person's question.
In general, when asking questions, the best thing is to provide relevant information for the people who will answer the question. For example, a person could ask themself:
"Where is the source of the content that caused my question?"
"What specific part of this source caused me to have this question?"
"What do I already know about my question?"
"Has prior research been helpful?"
"What solutions have i tried so far?"
If you include the answer to any of these questions in the context of a question you post, that will also help. You don't have to include the answer of all of them - a person might not even know the answer to all of them, because their question is very confusing or complicated.
Out Stack Exchange site also has a page that explains the qualities of good questions.