Ah, thanks for explaining - I was a little slow...
Yes, you can indeed add (enable) autolink functionality to TinyMCE with autolink plugin (if you change TinyMCE to your site default editor or select TinyMCE from your user profile to your editor).
You could edit file lib/editor/tinymce/lib.php and add to protected function get_init_params $params = array somewhere near line 135 for example
'plugins' => 'autolink,lists,table,style,layer,advhr,advlink,emotions,inlinepopups,' .
or you could simply go to Site administration > Plugins > Text editors > TinyMCE HTML editor > General settings and add to Custom configuration box
{"plugins" : "autolink"}
This plugin simply searches urls from editor content area and adds the link tags if the browser is not IE. Core developers should have no problems in creating a similar plugin for Atto if they see it necessary so adding a new feature request to tracker is ok. If I am not wrong there might not be such plugin for Atto available yet...
But IE is really the only browser doing this without asking your permission or coding tricks 
Here's the code of tinymce autolink plugin:
(function() {
tinymce.create('tinymce.plugins.AutolinkPlugin', {
/**
* Initializes the plugin, this will be executed after the plugin has been created.
* This call is done before the editor instance has finished it's initialization so use the onInit event
* of the editor instance to intercept that event.
*
* @param {tinymce.Editor} ed Editor instance that the plugin is initialized in.
* @param {string} url Absolute URL to where the plugin is located.
*/
init : function(ed, url) {
var t = this;
// Add a key down handler
ed.onKeyDown.addToTop(function(ed, e) {
if (e.keyCode == 13)
return t.handleEnter(ed);
});
// Internet Explorer has built-in automatic linking for most cases
if (tinyMCE.isIE)
return;
ed.onKeyPress.add(function(ed, e) {
if (e.which == 41)
return t.handleEclipse(ed);
});
// Add a key up handler
ed.onKeyUp.add(function(ed, e) {
if (e.keyCode == 32)
return t.handleSpacebar(ed);
});
},
handleEclipse : function(ed) {
this.parseCurrentLine(ed, -1, '(', true);
},
handleSpacebar : function(ed) {
this.parseCurrentLine(ed, 0, '', true);
},
handleEnter : function(ed) {
this.parseCurrentLine(ed, -1, '', false);
},
parseCurrentLine : function(ed, end_offset, delimiter, goback) {
var r, end, start, endContainer, bookmark, text, matches, prev, len;
// We need at least five characters to form a URL,
// hence, at minimum, five characters from the beginning of the line.
r = ed.selection.getRng(true).cloneRange();
if (r.startOffset < 5) {
// During testing, the caret is placed inbetween two text nodes.
// The previous text node contains the URL.
prev = r.endContainer.previousSibling;
if (prev == null) {
if (r.endContainer.firstChild == null || r.endContainer.firstChild.nextSibling == null)
return;
prev = r.endContainer.firstChild.nextSibling;
}
len = prev.length;
r.setStart(prev, len);
r.setEnd(prev, len);
if (r.endOffset < 5)
return;
end = r.endOffset;
endContainer = prev;
} else {
endContainer = r.endContainer;
// Get a text node
if (endContainer.nodeType != 3 && endContainer.firstChild) {
while (endContainer.nodeType != 3 && endContainer.firstChild)
endContainer = endContainer.firstChild;
// Move range to text node
if (endContainer.nodeType == 3) {
r.setStart(endContainer, 0);
r.setEnd(endContainer, endContainer.nodeValue.length);
}
}
if (r.endOffset == 1)
end = 2;
else
end = r.endOffset - 1 - end_offset;
}
start = end;
do
{
// Move the selection one character backwards.
r.setStart(endContainer, end >= 2 ? end - 2 : 0);
r.setEnd(endContainer, end >= 1 ? end - 1 : 0);
end -= 1;
// Loop until one of the following is found: a blank space, , delimeter, (end-2) >= 0
} while (r.toString() != ' ' && r.toString() != '' && r.toString().charCodeAt(0) != 160 && (end -2) >= 0 && r.toString() != delimiter);
if (r.toString() == delimiter || r.toString().charCodeAt(0) == 160) {
r.setStart(endContainer, end);
r.setEnd(endContainer, start);
end += 1;
} else if (r.startOffset == 0) {
r.setStart(endContainer, 0);
r.setEnd(endContainer, start);
}
else {
r.setStart(endContainer, end);
r.setEnd(endContainer, start);
}
// Exclude last . from word like "www.site.com."
var text = r.toString();
if (text.charAt(text.length - 1) == '.') {
r.setEnd(endContainer, start - 1);
}
text = r.toString();
matches = text.match(/^(https?:\/\/|ssh:\/\/|ftp:\/\/|file:\/|www\.|(?:mailto
?[A-Z0-9._%+-]+@)(.+)$/i);
if (matches) {
if (matches[1] == 'www.') {
matches[1] = 'http://www.';
} else if (/@$/.test(matches[1]) && !/^mailto:/.test(matches[1])) {
matches[1] = 'mailto:' + matches[1];
}
bookmark = ed.selection.getBookmark();
ed.selection.setRng(r);
tinyMCE.execCommand('createlink',false, matches[1] + matches[2]);
ed.selection.moveToBookmark(bookmark);
ed.nodeChanged();
// TODO: Determine if this is still needed.
if (tinyMCE.isWebKit) {
// move the caret to its original position
ed.selection.collapse(false);
var max = Math.min(endContainer.length, start + 1);
r.setStart(endContainer, max);
r.setEnd(endContainer, max);
ed.selection.setRng(r);
}
}
},
/**
* Returns information about the plugin as a name/value array.
* The current keys are longname, author, authorurl, infourl and version.
*
* @return {Object} Name/value array containing information about the plugin.
*/
getInfo : function() {
return {
longname : 'Autolink',
author : 'Moxiecode Systems AB',
authorurl : 'http://tinymce.moxiecode.com',
infourl : 'http://wiki.moxiecode.com/index.php/TinyMCE:Plugins/autolink',
version : tinymce.majorVersion + "." + tinymce.minorVersion
};
}
});
// Register plugin
tinymce.PluginManager.add('autolink', tinymce.plugins.AutolinkPlugin);
})();
