cleanup of Merge docstring

Author: erikvansebille

docs/user_guide/examples/tutorial_interaction.ipynb

@@ -279,30 +279,30 @@
     "    i_idx = np.arange(N)\n",
     "    mutual = has_nn & (nn[nn] == i_idx)\n",
     "\n",
-    "    # process each mutual pair only once (i < j)\n",
+    "    # define pairs i and their nearest neighbour j\n",
     "    pair_mask = mutual & (i_idx < nn)\n",
     "    pair_i = i_idx[pair_mask]\n",
     "    pair_j = nn[pair_mask]\n",
     "\n",
     "    if pair_i.size == 0:\n",
     "        return\n",
     "\n",
-    "    # larger = where mass_j >= mass_i -> j else i\n",
+    "    # compute which of the two (i, j) has the largest mass\n",
     "    mass_i = particles.mass[pair_i]\n",
     "    mass_j = particles.mass[pair_j]\n",
     "    larger_idx = np.where(mass_j > mass_i, pair_j, pair_i)\n",
     "    smaller_idx = np.where(mass_j > mass_i, pair_i, pair_j)\n",
     "\n",
     "    # perform transfer and mark deletions\n",
-    "    # note that we use temporary arrays for indexing because of KernelParticle bug (GH #2143)\n",
+    "    # TODO note that we use temporary arrays for indexing because of KernelParticle bug (GH #2143)\n",
     "    masses = particles.mass\n",
     "    states = particles.state\n",
     "\n",
     "    # transfer mass from smaller to larger and mark smaller for deletion\n",
     "    masses[larger_idx] += particles.mass[smaller_idx]\n",
     "    states[smaller_idx] = parcels.StatusCode.Delete\n",
     "\n",
-    "    # TODO use particle variables directly KernelParticle bug (GH #2143) is fixed\n",
+    "    # TODO use particle variables directly after KernelParticle bug (GH #2143) is fixed\n",
     "    particles.mass = masses\n",
     "    particles.state = states"
    ]