This mod is essentially a revamped Don't Deselect, with many extra features and improved compatibility.
Requires Mod Options Framework
If you disable this mod, and are having problems with double-select-centering, go into the console (ctrl+f8) and enter "cg_cmdrDoubleSelectTime 500" without the quotes.
Download:
Requires HoN Mod Manager and Mod Options Framework
v1.80: locktarget.honmod
Features:
Don't Deselect
When your currently selected target enters the fog or becomes invisible, it won't be deselected. This allows you to continue to view that target's items/health/mana.
(Note, this will NOT update the target's information. It simply shows the information from the last time the target was visible.)
When the target is visible and active (and the target's information is being updated), the UI looks like this:

When the target is not visible, it is inactive (and the target's information is NOT being updated), the UI looks like this:

Press ESC, or whatever key you rebound it to, to clear the target, and display the normal command buttons.
Automatic Reselect
If your selected target enters the fog, and then later re-emerges, this mod will automatically reselect him.
The same applies to invisibility. If your target goes invisible, this mod will reselect him as soon as he becomes visible.
Attack Target Hotkey
This mod adds a rebindable-hotkey to the game options. This hotkey is called "Attack Target"
When you press this hotkey, your hero will automatically try to attack the target you have selected.
Also, if you are currently choosing the target of an ability (ie. you are using the cross-hair cursor), and you press this hotkey, your hero will automatically use that ability on your selected target.
Announce Target Hotkey
This will display the name of the current target in Team Chat
Known Issues
Code:
-The attack/move icons are greyed out. This is to prevent a bug that would occur if you click them. To move/attack, use a hotkey.
-Double-select-centering is disabled (other than for your hero) when your target is inactive.
Changelog
Code:
v1.80
-All Right Click Deny functionality removed.
v1.70
-Updated for HoN v1.0.0
v1.60
-Integrated Right Click Deny
-Moved the hotkeys to Mod Options Framework
-Added announce target hotkey
-Fixed a bug with left-click becoming nonresponsive
v1.51
-Fixed a bug with left clicking while in spectator
v1.50
-Updated for FE2
v1.40
-Fixed another control bug
-Double selecting your hero will now center the camera correctly.
v1.30
-Fixed a bug that prevented you from controlling Wildsoul's bear or ophelia's creeps
v1.2
-Fixed a bug that caused your hero to freeze when you issue attack/move/patrol commands
-Fixed a bug with conflicting hotkeys
-Fixed a bug that caused an annoying clicking sound to loop when the target is inactive
v1.1
-Fixed a bug that would cause a spam of "Invalid Target" when your target was inactive.
-This mod will no longer permanently set cg_cmdrDoubleSelectTime to 0
-Fixed a bug that allowed the Attack Target hotkey to work when you have no target selected.
v1.0
-Initial release