topic.asp line 679 should look like this:
" <td valign=""bottom""><hr noshade size=""" & strFooterFontSize & """><font color=""" & strForumFontColor & """ face=""" & strDefaultFontFace & """ size=""" & strDefaultFontSize & """><span class=""spnMessageText"">" & formatStr(Reply_MemberSig) & "</span></font></td>" & vbNewLine & _
Make it look like this (changed parts are red):
" <td valign=""bottom""><br /><hr noshade size=""" & strFooterFontSize & """><font color=""" & strForumFontColor & """ face=""" & strDefaultFontFace & """ size=""" & strFooterFontSize & """><span class=""spnMessageText"">" & formatStr(Reply_MemberSig) & "</span></font></td>" & vbNewLine & _
If your FooterFontSize is larger than 1, you can also replace size=""" & strDefaultFontSize & """ with size=""1""
Line 881 looks pretty much the same as the one above, the same changes should be applied there too.
Make a backup of your files before you make any changes in case you need to undo the changes!