Twoots controller:

  def comment_like
    @twoot = Twoot.find(params[:id])
    @comment = NO IDEA WHAT TO PUT THERE
    current_user.favorite(@comment)
    redirect_to twoot_path(@twoot)
  end

  def comment_unlike
    @twoot = Twoot.find(params[:id])
    @comment = SAME, NO IDEA
    current_user.remove_favorite(@comment)
    redirect_to twoot_path(@twoot)
  end


Views:
<% @comments.each do |comment| %>
...
<% if user_signed_in? %>
  <% if comment.favorited_by?(current_user) %>
    <%= button_to 'Unlike', {action: "comment_unlike" }, { class: "btn waves-effect hoverable red lighten-2" } %>
   <% else %>
    <%= button_to 'Like', {action: "comment_like" }, { class: "btn waves-effect hoverable red lighten-2" } %>
<% end %>
<% end %>
<% end %>