Take a look at my comment here
rule34.xxx/index.php?page=post&s=view&id=903274

It seems that when you attempt to link something with another URL in it...it confuses the hell out of it.

Obviously, you are trying to make an html link ;/

you can not insert html, we partially support bb code i think.

You can just use tinyurl.com to make it short enough to put in the comments :)

The brackets could be a problem, too. The closing bracket can be erroneously interpreted as part of the link in some (partially-)BBCode-enabled board software.