Reproduced with php 5.5 and php 5.6 (built with homebrew as well)

I cannot tell what implication this workaround / fix will have, but I've verified that
in ezpublish-kernel/eZ/Bundle/EzPublishDebugBundle/Twig/DebugTemplate.php, if
$templateResult = ob_get_clean(); is changed to
$templateResult = html_entity_decode( ob_get_clean() );, the image renders properly (while in DEV mode)

Might this be considered a valid fix? That being the case I would be happy to create a PR

(Found this on stackoverflow: http://stackoverflow.com/questions/10062780/preserving-html-entities-with-libxml)

I've been trying to identify where to fix the issue for PROD environment, so far without success. But since I only use OSX for DEV, I've adapted the above workaround in my local installation for the time being.

is there any update on this?

for the time being I created this jquery helper which I can run in browser dev tools but a real fix would be appreciated

$(".ezrichtext-field").contents().filter(function(){return this.nodeType === 3 && $.trim(this.nodeValue) !== '';}).each(function(){$(this).replaceWith(this.textContent)});

Io Sol Inf If several can confirm the fix and with no side effects for others we are happy to accept a PR. Make sure to yo add inline comment on why it is done like that

André Rømcke, I don't thibnk that my hack can be applied in production. If I recall correctly, it solved the issue in DEV but it seems to much "hackish" to be applied in PROD.
I'll check if the issue still exists with the latest eZPlatform / OSX updates.

It still exists on eZ Platform 1.9.0-rc1, at least. And the fix you have suggested still works.
Note that your fix doesn't apply to the prod environment, as the DebugTemplate class is only used in prod. The annoying part is that it only affects some setups, not all.

I continued to experience this issue with PHP 7.1.4 package from Brew on Mac OS X (10.11.16). I tried a few different things to try to update the package to use a newer libxml2/libxslt versions, but didn't get it to work it. For now me the easiest solution was to replace the Brew PHP package with the LIIP one from https://php-osx.liip.ch.

Version details, etc. here: http://share.ez.no/forums/ez-platform/ez-platform-image-embed-output-escaped-on-macos-os-x/(offset)/last