I encountered the bug in the text area Description. Now, I encounter the bug in the text area Comment too.

In T128309#2070653, @Aklapper wrote:

The trivial workaround is to literally write **. See https://secure.phabricator.com/book/phabricator/article/remarkup/

This workaround does exist. But the user has to know it. I wanted the button because I had forgotten what the code was for bold.

Are there particular reasons why a certain button (Bold) is more important than another certain button (like List or Table)?

I don't see either the buttons List nor Table.

It's not that all the buttons shown in Desktop view would fit in Mobile view

Maybe they would fit.

There is much empty space in the bar of buttons. More than half of the bar of buttons is empty.

At least, the button for bold and several other buttons would fit.

And, in full page, all buttons would surely fit!

In full page, more than 77 % of the bar of buttons are empty, I measured, there are more than 10 cm free in the bar!

hence you have to make a cut somewhere

No, you do not have to. There is much empty space in the bar of buttons. Especially in full page!

It's highly inconsistent behavior actually:

On some devices, or on some view sizes, the Web app becomes unduly crippled. This is an accessibility issue.

Thank you Danny for the table!