Here is how . . . type everything you want (crossed out words and not) then click on the edit HTML button and add these 3 characters directly in front of the word you want crossed out.
the open arrow < the letter s and the closed arrow >
all with no spaces in between
Then at the end of what you want crossed out you type these 4 characters.
the same open arrow < but this time with a backslash / and then an s and then a closed arrow >
again . . . NO SPACES.