Or, if you only want to remove the line breaks in one place, write the tag as follows:
CODE
<$MTCommentBody convert_breaks="0"$>
This will turn off the conversion of line breaks only in the one place, while leaving it on globally. For instance, I like to have it on in the comment listing template so my visitors don't have to use [p] tags when they write their comments, but in some places that I display the comments I don't want the line breaks, so then I use the "convert_breaks" attribute.