Pull request notifications coming in seem about 50/50 split between rendered and raw markdown. Most of our pull request descriptions start with a link followed by a heading, so we see a mix of the properly rendered markdown along with notifications that look like:
[the link](https://the-url.com)
### The heading
...
@bkeepers @wilhelmklopp it's possible this occurs when updating an existing message with pull request statuses and the like. Haven't been able to watch it happen live just yet 馃槃
@daneah yeah that's pretty much spot on! We've identified the cause for the bug and are figuring out a solution.
Some investigation is going on in #425
this has been happening for our team for PR descriptions and replies containing images. We rely on these images for morale! Many of them are of squirrels!
We have noticed that markdown is not rendered on our repos that have continuous integration

And when there is no hook for the CI its fine:

@olivierGM I think that is more evidence for the hypothesis above:
it's possible this occurs when updating an existing message with pull request statuses and the like.
This is happening on issues as well for us as well as PR.
this has been happening for our team for PR descriptions and replies containing images. We rely on these images for morale! Many of them are of squirrels!
@pklingem the issue that tracks images is here: https://github.com/integrations/html-to-mrkdwn/issues/2
This is happening on issues as well for us as well as PR.
@stevesuh Could you open a separate issue for this with steps to reproduce? Thanks 馃檱
I see that this issue has been closed as resolved, but I am still seeing the reported behavior in comments, as seen below, from https://bisq.slack.com/archives/C7UHH8UQM/p1521038700000431:

Shall I open a separate issue for this?
Images don't seem to be showing up in GH comments:

@nickbouton that'd be great, thanks!
^ @cbeams, that is 馃槢
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this has been happening for our team for PR descriptions and replies containing images. We rely on these images for morale! Many of them are of squirrels!