Hey Jaime,
What you trying is a security risk. It is not clever to let users input html code on your site - they can make some pretty nasty stuff.
That is why in all kind of forums and comments you have bbcode.
In your case you just need write the url, selecte it and click the url button. Or just write
[url]
index.php?option=com_hum&view=proyecto&id=nn:yyy
[/url]
this will transform the text to <a href="index.php?option=com_hum&view=proyecto&id=nn:yyy">index.php?option=com_hum&view=proyecto&id=nn:yyy</a>
if you want to have text
then write
[url=index.php?option=com_hum&view=proyecto&id=nn:yyy] my text [/url]
and this will be transformed to <a href="index.php?option=com_hum&view=proyecto&id=nn:yyy">my text</a>