No seen any docs on it but I did a few tests a while ago and it picks up, subject, from, and text in the body and alt text.
But not any aria- attributes, I though aria-label might show up but it didn't.
There are a number of browser plugins available that block pixel tracking, often these are bundled as part of a larger Ad Block plugin. That could be what's causing the issue on the webmail clients.
I believe you can add a type="gradient" to <v:fill> not done much testing on it, just saw someone share it and made a note.
https://docs.microsoft.com/en-us/windows/desktop/vml/angle-attribute--fill--vml
There's nothing wrong with <script> tags it's more the contents of them that can be an issue, but some ESP's do insist on removing them everytime.
With the new Gmail annotations you have a choice of JSON or Microdata, Freshinbox has a similar tool to Litmus that outputs Microdata so you could use that instead.
http://freshinbox.com/blog/gmails-promotion-card-and-promotion-tab-changes
Do you have any sample code you can share that is triggering the bug?
One other possible thing, do you have images turned off?
If so when images are loaded there is a bug that the CSS no longer matches the HTML so no styles will work.
Strange, that's working fine for me, I quickly swapped the background colour to make it easier to see and the gmail one is definitely showing on Gmail.
As a side note, if you wanted to get the same layout in Gmail try adding max-height: 0;margin-top:15px; to the same div that has the class="gmail" and it'll flow over the next section.
Yeah i think there should be a share function at the top of builder that will give you a link to share
Or you can past code in here with three backticks either side of it
code