Paper:
Many practical robot locomotion tasks require agents to use control policies that can be parameterized by goals. Popular deep reinforcement learning approaches in this direction involve learning goal-conditioned policies or value functions, or Inverse Dynamics Models (IDMs). IDMs map an agent's current state and desired goal to the required actions. We show that the key to achieving good performance with IDMs lies in learning the information shared between equivalent experiences, so that they can be generalized to unseen scenarios. We design a training process that guides the learning of latent representations to encode this shared information. Using a limited number of environment interactions, our agent is able to efficiently navigate to arbitrary points in the goal space. We demonstrate the effectiveness of our approach in high-dimensional locomotion environments such as the Mujoco Ant, PyBullet Humanoid, and PyBullet Minitaur. We provide quantitative and qualitative results to show that our method clearly outperforms competing baseline approaches.

Review:
The paper proposes a method for exploiting structure in locomotive tasks for efficiently learning low-level control policies that pass through waypoints while achieving some goal (typically 3D Cartesian position). This is in contrast to goal-conditioned RL policies that sample random goals during training and are thus sample inefficient, which are trained to execute one policy at a time. In particular, the paper proposes the notion of generalized experiences, where new trajectories are generated from existing trajectories, in such as a way that they are equivalent to each other (in this case translation and orientation invariant) with respect to actions.  
The idea proposed here, of exploiting environmental structures in order better generalize previous knowledge to new, unseen situations is an interesting direction for achieving sample efficiency in practical RL, such as in robotics. 
I have the following comments/questions.
1. If I understand correctly, rather than randomly sampling the environment, the paper proposes starting off with trajectories generated while learning some single-goal policy, and generate from these new ones that the agent must execute in the environment. In which case, the question is how much less interaction does the agent have with the environment compared to random goal sampling, to achieve the same performance?
2. What happens if you use a standard goal-conditioned RL with the Generalized Experiences, without training an IDM? For example, using VGCP with GE, where the goals for VGCP are teminating states of each trajectory. In other words, can a vanilla goal-conditioned RL benefit from the proposed trajectory sampling technique (GE), and how does that compare with random sampling and using the proposed latent representation technique?
3. How do you modify the LFM so that it only accepts the current state and goal, instead of a set of two e.m.o equivalent states and goals? Is the same query treated as two queries that are e.m.o equivalent?
4. In A.1.2, the paper mentions that the first half of the data generated using the RL algorithm is used for generating the second half of data for GE and LR, right? Which means GE and LR are trained from the same number of steps as the baselines, except that GE and LR make use of generalized experiences. However, the paper states in A2 that GE and LR learn from inferior samples. Can the authors please clarify this? My understanding is that GE are generated by modifying existing trajectories and letting the agent apply the same actions by interating with environment. Meaning that, given 2M samples, GE will generate 2M more samples that are e.m.o equivalent by interacting with the environment. 
5. Some of the references in the text do not have year of publication, e.g., Kulkarni et al.