Expanding a question's scope vs. Starting a new question

Question

Sometimes, there's a question that almost answers one that you have. Perhaps the title is similar, or the other question specifically excludes a point that you're interested in.

For an example case, this old question, about PNP transistors, has an answer about their operation accepted without comment. It doesn't mention the physics behind the behavior, but Federico wants to know this information.

What should be done here? There are a few options:

1. Ask your question, explaining the differences between yours and the [preferably linked] pre-existing question.
2. Edit the previous question to include yours.
3. Ask the poster of the previous question whether they'd like to include your topic, and take option 1 or 2 based on the result of this communication. Note that this may take some time (or never happen) if the OP doesn't visit regularly.

My opinion is currently quite firmly fixed on option 1, but I'd be interested to hear arguments from all sides.

Answer 1

Favor Option 1

If the OP accepted an answer we must assume that it was done because the answer actually did answer the question.

If we go off of the assumption above, editing the previous question would be adding to it in a way that didn't really make any difference to the OP and could cause someones really good answer to become not so good. It is difficult to get people to come revisit a question after it has an accepted answer.

Answer 2

I think this is really a judgment call; options 1 or 2 are both valid depending on the circumstances.

If you strongly feel option 1 is the best fit, go for that.