Thank you for your reply. Yes, a know about MathJax. I mean that there happens some unnecessary unescaping, where double backslash (meaning start of new line in LaTeX) is replaced by single one (which is treated as space in mathmode).
I tried for the align (ams) LaTeX environment, the same holds for other multiline math enveronments like eqnarray, gather, multline.
1 I enter sample two-line formula, and see that it is correctly rendered by MathJax
Unfortunately, as a new user I an allowed to add only one screenshot. Futher screenshot available on demand
2. But on the “Call for abstracts” page the result is wrong - the two formulas are in a single line.
3.Right-click the formula to see the LaTeX source.
4. And noitice that only one backsjash survived - thus we see space instead of new line.
5 Edit the source and add two extra backslashes - visually added more space between fomulas.
6.Now the result is nice - two-line formula as needed.
7. Right-click formula to check the source and see two backslashes as it should be.