This one took me a while to find (in my case). I assumed it was not possible and was lazy to look around. But, after wearing my irregular bucket hat I decided to go for it.
I found it! and it was very simple. If you need to comment within a Jinja2 template you need to use {# #} tags. For example:
{# {{ Hello Hello soyhat.com }} #}
I have been trying the below and never worked for me:
<!-- {{ Hello hello }} -->
I still have a long way to go before I can feel comfortable building my web app using Flask. I will not give up. Contact me if you have any questions. Remember to check out my designs below.