Moral philosophy is discussed in effective altruism for a number of different reasons. 

In some cases, discussions about moral philosophy focus on related topics like: 

• How can one measure or compare value? This often focuses on different theories of wellbeing (what is good for a being, questions about non-wellbeing sources of value, more generally what has intrinsic value,  etc.)
• Which animals (or other beings) are moral patients — whether they have the capacity for welfare (and how much), and how we should study this question
• Comparisons between deontology and consequentialism, the difference between naive vs. sophisticated consequentialism, etc.
• Theories like longtermism, which is the view that positively influencing the long-term future is a key moral priority of our time
• The philosophy of effective altruism