Currently we allow the following HTML tags in comments:
Single tags
These tags can be used alone and don’t need an ending tag.
br Defines a single line break
hr Defines a horizontal line
Matching tags
These require an ending tag – e.g. iitalic text/i
a Defines an anchor
b Defines bold text
big Defines big text
blockquote Defines a long quotation
caption Defines a table caption
cite Defines a citation
code Defines computer code text
em Defines emphasized text
fieldset Defines a border around elements in a form
h1 This is heading 1
h2 This is heading 2
h3 This is heading 3
h4 This is heading 4
h5 This is heading 5
h6 This is heading 6
i Defines italic text
p Defines a paragraph
pre Defines preformatted text
q Defines a short quotation
samp Defines sample computer code text
small Defines small text
span Defines a section in a document
s Defines strikethrough text
strike Defines strikethrough text
strong Defines strong text
sub Defines subscripted text
sup Defines superscripted text
u Defines underlined text
Article source: http://www.informationweek.com/news/cloud-computing/software/231903004