<li class="suggestion">
  <aside>
    <div class="vote-count" data-id="<%= suggestion.id %>">
      <%= suggestion.vote_count %>
    </div>

    <div class="vote" data-id="<%= suggestion.id %>">
      <% if vote_for_suggestion %>
        <%= semantic_form_for vote_for_suggestion, html: { method: :delete } do |f| %>
          <%= f.input :suggestion_id, as: :hidden, input_html: { value: suggestion.id } %>
          <%= f.action :submit, button_html: { value: "✔" } %>
        <% end %>
      <% else %>
        <%= semantic_form_for suggestion.votes.build do |f| %>
          <%= f.input :suggestion_id, as: :hidden, input_html: { value: suggestion.id } %>
          <%= f.action :submit, button_html: { value: "✔" } %>
        <% end %>
      <% end %>
    </div>
  </aside>
  <div class="description">
    <%= suggestion.description %>
  </div>
</li>

<li class="suggestion">
  <aside>
    <div class="vote-count" data-id="<%= suggestion.id %>">
      <%= suggestion.vote_count %>
    </div>

      <% if vote_for_suggestion %>
        <div class="vote undo-vote" data-id="<%= suggestion.id %>">
          <%= semantic_form_for vote_for_suggestion, html: { method: :delete } do |f| %>
            <%= f.input :suggestion_id, as: :hidden, input_html: { value: suggestion.id } %>
            <%= f.action :submit, button_html: { value: "✔" } %>
          <% end %>
        </div>
      <% else %>
        <div class="vote" data-id="<%= suggestion.id %>">
          <%= semantic_form_for suggestion.votes.build do |f| %>
            <%= f.input :suggestion_id, as: :hidden, input_html: { value: suggestion.id } %>
            <%= f.action :submit, button_html: { value: "✔" } %>
          <% end %>
        </div>
      <% end %>
  </aside>
  <div class="description">
    <%= suggestion.description %>
  </div>
</li>

Add additional css class 'undo-vote' to votes which can be undone
Add additional css class 'undo-vote' to votes which can be undone
