When should a writer worry about subtexting? Is it important?
Subtexting adds layers and depth to a story, well at least to the characters. Subtexting is that hidden psychological meaning behind what is said or done by a character. It's all about history. The more history a character has with another character the deeper the subtext between them will be. Each minor argument or conflict will have years of history and arguments behind it. The trick is figuring out how to get that subtext out and onto the page.
You can do this through action, reaction, a few chosen words, mannerisms, inner monologue, the playing with a prop, and symbolism.
What in the scene can symbolize the subtextual meaning of this scene, for example.
Or what is the character really thinking at that moment?
Or does a certain word evoke a particular memory for one character?
Or does one character seem to over react to what is being said?
Answering 'why' can help you find the subtext. You may even go back and create a history between two characters to make the scene more lively.