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

Arefly

Use <a href="http://en.wikipedia.org/wiki/BBCode" rel="nofollow ugc">BBCode</a> in posts or comments.
讓你可以在部落格中使用 <a href="http://en.wikipedia.org/wiki/BBCode" rel="nofollow ugc">BBCode</a>
Examples:
<pre><code>Bold: [b]bold[/b]

Italics: [i]italics[/i]

Underline: [u]underline[/u]

Delete: [del]delete[/del]

Code: [code]some code...[/code]

Font Color: [color="red"]These words are red![/color]

Font Size: [size="20"]These words are font size 20px big![/size]

Center: [center]These words are in the center![/center]

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]

URL: [email="info@google.com"]Send Mail To Google[/email] [email]info@google.com[/email]

Quote:

[quote]Lorem ipsum dolor sit amet, consectetuer adipiscing elit, sed diam nonummy nibh euismod tincidunt ut laoreet dolore magna aliquam erat volutpat. Ut wisi enim ad minim veniam, quis nostrud exerci tation ullamcorper suscipit lobortis nisl ut aliquip ex ea commodo consequat. Duis autem vel eum iriure dolor in hendrerit in vulputate velit esse molestie consequat, vel illum dolore eu feugiat nulla facilisis at vero eros et accumsan et iusto odio dignissim qui blandit praesent luptatum zzril delenit augue duis dolore te feugait nulla facilisi.[/quote]

Textarea: [textarea]This is something in a textarea![/textarea]

Table:
[table]
[tr]
[th]row 1, title 1[/th]
[th]row 1, title 2[/th]
[/tr]
[tr]
[td]row 2, cell 1[/td]
[td]row 2, cell 2[/td]
[/tr]
[tr]
[td]row 3, cell 1[/td]
[td]row 3, cell 2[/td]
[/tr]
[/table]

Note: (The content in note will not display)

[note]These words will not display on the screen.[/note]

Line: (It will just display a line, and you should not add anything into it.)

[line][/line]

Unordered List: 

[ul]
[li]First Item[/li]
[li]Second Item[/li]
[/ul]

Ordered List: 

[ol]
[li]First Item[/li]
[li]Second Item[/li]
[/ol]

Right Align Text: [rtl]These Text are on the right![/rtl]
</code></pre>
<h4>Translators</h4>
<ul>
<li>Chinese, Simplified (zh_CN) – <a href="http://www.arefly.com/" rel="nofollow ugc">Arefly</a></li>
<li>Chinese, Traditional (zh_TW) – <a href="http://www.arefly.com" rel="nofollow ugc">Arefly</a></li>
<li>English (en_US) – <a href="http://www.arefly.com" rel="nofollow ugc">Arefly</a></li>
</ul>
If you have created your own language pack, or have an update of an existing one, you can send <a href="https://codex.wordpress.org/Translating_WordPress" rel="nofollow ugc">gettext PO and MO files</a> to <a href="http://www.arefly.com/about/" rel="nofollow ugc">Arefly</a> so that I can bundle it into WP BBCode. You can download the latest <a href="https://plugins.svn.wordpress.org/wp-bbcode/trunk/lang/wp-bbcode.pot" rel="nofollow ugc">POT file</a>.

WP BBCode

Use BBCode in posts or comments. 讓你可以在部落格中使用BBCode

BBComments vs WP BBCode