<p>I believe I found it: <a href="https://stats.stackexchange.com/questions/279209/vanishing-gradient-vs-dying-relu">Vanishing gradient vs. dying ReLU?</a> (youtube video <a href="https://www.youtube.com/watch?v=l1YxQ1Od1Y0" rel="nofollow noreferrer">here</a>).</p>

<p>The reason you probably did not find the comment is because it was not <code>shimao</code> who posted, but <code>Jan Kukacka</code> (see <a href="https://stats.stackexchange.com/questions/279209/vanishing-gradient-vs-dying-relu#comment608229_279209">here</a>).</p>

<blockquote>
  <p><sub> I recommend watching this talk by Moritz Hardt (youtube.com/watch?v=l1YxQ1Od1Y0) where he explains that ReLU in fact does not solve the vanishing gradient problem. – Jan Kukacka Dec 25 '17 at 20:20 </sub></p>
</blockquote>

<p>I found the question putting the following in CV's search box: <code>vanishing gradient problem ReLU</code> (it was the first/top Q in the 'relevance' tab).</p>
