Basic strikethrough is between two tildes:
~~This is *stricken out*~~
.
<p><del>This is <em>stricken out</em></del></p>
One tilde does nothing:
~This is nothing~
.
<p>~This is nothing~</p>
Backslash escapes:
~~This is \~\~stricken~~
.
<p><del>This is ~~stricken</del></p>
Intraword strikeout:
This~~is~~stricken
.
<p>This<del>is</del>stricken</p>
~~This~~is~~stricken~~
.
<p><del>This</del>is<del>stricken</del></p>
Punctuation is ignored for purposes of determining flankingness:
Here I strike out an exclamation point~~!~~.
.
<p>Here I strike out an exclamation point<del>!</del>.</p>