Cannot underline a text in markdown

It seems that we cannot use markdown to underline text, and should use either or .

• Can we confirm that there is no underline in markdown ?
• If not, add it to the white list

spotted by @npietros

added UX label

mentioned in commit 13c99f13

mentioned in commit aba5c44a

mentioned in commit 7802582f

mentioned in commit 91311ef3

closed with commit 7802582f