user7508: I usually use fenced code blocks in order to get code
syntax-highlighted, as in
```c++
some C++ source
```

This used to work for quite some time. However, since a couple of days
or so, it looks like it doesn't work anymore.
Examples: here and here.
The weird thing is: while editing, the syntax highlighting does work in
the preview... sometimes!
Did I do something wrong? Is this feature deprecated? Is it just a
glitch in the Matrix?

user7508: As mentioned by VE7JRO, the language can be specified using a
specially-formatted HTML comment.
For those who prefer the more standard “fenced code blocks”, my tests
show they still work when the fence is labeled cpp or lang-cpp, but
not with the labels c++ or lang-c++:
```cpp
for (int i = 0; i < 42; i++)  // be insistent
    Serial.println("Hello!");
```

is rendered:
for (int i = 0; i < 42; i++)  // be insistent
    Serial.println("Hello!");

Edit: This may be the cause of the issue:
We're switching to CommonMark.

user37523: I removed the c++ in the first question, and now the syntax highlighting is working.
If it worked before (with the c++), my best guess is Stack Exchange made some changes in the back end.
There is another way to force syntax highlighting for all code blocks in a particular Q or A.
<!-- language-all: lang-cpp -->

There is more information here: Markdown help, and according to this page, the c++ should work.
Clearly there is something wrong or something changed. I'll see what I can find out...

7508: <p>I usually use fenced code blocks in order to get code
syntax-highlighted, as in</p>
<pre><code>```c++
some C++ source
```
</code></pre>
<p>This used to work for quite some time. However, since a couple of days
or so, it looks like it doesn't work anymore.</p>
<p>Examples: <a href="https://arduino.stackexchange.com/a/76446/7508">here</a> and <a href="https://arduino.stackexchange.com/a/76397/7508">here</a>.</p>
<p>The weird thing is: while editing, the syntax highlighting does work in
the preview... sometimes!</p>
<p>Did I do something wrong? Is this feature deprecated? Is it just a
glitch in the Matrix?</p>
 7508: <p>As mentioned by VE7JRO, the language can be specified using a
specially-formatted HTML comment.</p>
<p>For those who prefer the more standard “fenced code blocks”, my tests
show they still work when the fence is labeled <code>cpp</code> or <code>lang-cpp</code>, but
not with the labels <code>c++</code> or <code>lang-c++</code>:</p>
<pre><code>```cpp
for (int i = 0; i &lt; 42; i++)  // be insistent
    Serial.println(&quot;Hello!&quot;);
```
</code></pre>
<p>is rendered:</p>
<pre class="lang-cpp prettyprint-override"><code>for (int i = 0; i &lt; 42; i++)  // be insistent
    Serial.println(&quot;Hello!&quot;);
</code></pre>
<p><strong>Edit</strong>: This may be the cause of the issue:
<a href="https://meta.stackexchange.com/questions/348746">We're switching to CommonMark</a>.</p>
 37523: <p>I removed the <code>c++</code> in the first question, and now the syntax highlighting is working.</p>
<p>If it worked before (with the <code>c++</code>), my best guess is Stack Exchange made some changes in the back end.</p>
<p>There is another way to force syntax highlighting for <strong>all</strong> code blocks in a particular Q or A.</p>
<pre><code>&lt;!-- language-all: lang-cpp --&gt;
</code></pre>
<p>There is more information here: <a href="https://stackoverflow.com/editing-help">Markdown help</a>, and according to this page, the <code>c++</code> <strong>should</strong> work.</p>
<p>Clearly there is something wrong or something changed. I'll see what I can find out...</p>
