Sorry but I have no idea what you are trying to ask.

You can do it by editig the core file \include\staff\profile.inc.php on line 408.
Change

<textarea class="richtext no-bar" name="signature" cols="21"

to this

<textarea class="richtext" name="signature" cols="21"

I recommend reconsidering whether this is a really good idea.

One better way:
File \js\redactor-osticket.js, line 258
From this
? ['formatting', '|', 'bold', 'italic',...
to this
? ['html', '|', 'formatting', '|', 'bold', 'italic',...