use simple BBCode in your comments 
atm follow tags available:
[b]bold[/b] 
[i]italic[/i] 
[u]underline[/u] 
[color=color]text[/color] example [color=FF6600]Text[/color]
list 
[ul] 
[li]number 1[/li] 
[li]number 2[/li] 
[li]number 3[/li] 
[/ul]
[url=http://www.google.com]Google[/url] 
[img=http://uri.to.pic][/img] (fix picsize)
(required wp-syntax) 
[code]your code[/code], 
optional with declaration of the language 
[code lang=”csharp”]your sample code[/code] (all available languages from wp-syntax possible)
<h3>Arbitrary section</h3>
Visit my blog for more nice wordpress plugins and .net tutorials and codes : )

BBComments

antonchanning

This plugin adds support for bbcode markup to wordpress, bbpress and buddypress. 
It integrates with the ‘bbPress shortcode whitelist’ plugin to provide a safe 
way of enabling BBCode without giving your users access to all shortcodes.
<pre><code>Bold: [b]bold[/b]
Italics: [i]italics[/i]
Underline: [u]underline[/u]
URL: [url]https://wordpress.org/[/url] [url=https://wordpress.org/]WordPress[/url]
Image: [img]https://s.w.org/style/images/codeispoetry.png[/img] [img=Code is Poetry]https://s.w.org/style/images/codeispoetry.png[/img]
Quote: [quote]Lorem ipsum dolor sit amet, consectetuer adipiscing elit,[/quote] [quote=NAME]Lorem ipsum dolor sit amet[/quote] [quote="NAME"]Lorem ipsum dolor sit amet[/quote] [quote author=NAME]Lorem ipsum dolor sit amet[/quote] [quote author="NAME"]Lorem ipsum dolor sit amet[/quote]
Color: [color="red"]named red[/color] [color="ff0000"]hex red[/color] [color=#ff0000]hex red again[/color]
Strikeout:[s]striked this out[/s]
Center Text:[center]center me[/center]
Computer code:[code]function HelloWorld($greet = 'World') { return 'Hello '.$greet } [/code]
Font size: [size=10]10px font size[/size]
Ordered lists: [ol][li][/li][/ol]
Unordered lists: [ul][li][/li][/ul]
List Item: [li]item[/li]
Named Spoiler: [spoiler=two plus two]four[/spoiler]
Unnamed Spoiler: [spoiler]Boo![/spoiler]
Contents appear to logged in users only: [user]This is a secret message[/user]
Contents appear to non-logged in users only: [guest]Log in to see secret message...[/guest]
</code></pre>
I have enhanced support for the [url] and [quote] tags, and added potentially 
useful css style class names in the html output of the tags, to allow for 
exciting theming potential.
For example:
<pre><code>[quote=NAME]QUOTE[/quote] 
</code></pre>
will render as:
<pre><code><div class="bbcode-quote bbcode-quote-NAME">NAME<blockquote>QUOTE</blockquote></div>
</code></pre>
Or if NAME matches the login name of a user on the system, it will render as:
<pre><code><div class="bbcode-quote bbcode-quote-user bbcode-quote-NAME">DISPLAY_NAME<blockquote>QUOTE</blockquote></div>
</code></pre>
Where DISPLAY_NAME is the display name that user. With BuddyPress installed the name 
also becomes a link to their profile page, otherwise if bbPress is installed, it becomes a 
link to their forum user page.

bbPress2 BBCode

This plugin adds support for popular bbcode forum code to posts, comments, pages, bbpress 2.0 forums and buddypress activity and group forums.

BBComments vs bbPress2 BBCode