If I write four asterisks in a row like this **** they will disappear as soon as the writing cursor is no longer on the line. When I put the cursor on the line again, the asterisks reappear.
If I do the same with one or two or three asterisks : no problem.
If I do the same with five asterisks, only one asterisk will remain visible.
If I do the same with six asterisks, only two asterisks will remain visible.
More generally, the biggest multiple of four asterisks will disappear. So if you write 9 asterisks, 8 asterisks will disappear. If you write 26 asterisks, 24 asterisks disappear.
iOS 11.0.2
iPhone 6s+
Dynalist app 1.1.22