In 5.4.1, the XSS security issue about html in markdown has been corrected. But, the feature could be really interesting...
Is there plan to offer the feature again using a configuration flag? Or after sanitising the html code ?
There are no plans for now.
But out of curiosity, what are you trying to accomplish using HTML there? Maybe we could offer a workaround.
Thx for the info, even if it doesn't fit my needs 
I have to display 3 textual informations in one viz:
- current value
- delta in % between last value and value last month
- delta in % between last value and value last year
Values 2. and 3. are displayed in red if negative, green if positive. It was easy to do with md+html+css in visual builder v5.4.0
It seems to me that the metric view display only the 2 first series configured in visual builder.
Ah, i think that can be done with field formatting as well. It works for all the other visualizations, I'd assume it would work for Visual Builder too.