If you have to be a pedant and tell people to use a multiplication symbol, then use a multiplication symbol. The symbol is × (×), not the letter X.
If you want to be a better pedant, you better start paying attention, like for example to the fact that I alluded to x not being the multiplication symbol by a) putting it in quotes and b) writing ~ "x", where ~ is the well known "approximately equal to" math symbol.