IMP 7.0.

Changes have been made in Git (master):

commit 3e0131a16105d0e387d1369b2fcb1c0f3891174a
Author: Michael M Slusarz <slusarz@horde.org>
Date:   Wed Dec 3 16:00:25 2014 -0700

     Provide visual distinction between checkbox hover and checkbox on 
(Request #13203)

  imp/themes/default/graphics/checkbox_over.png |  Bin 468 -> 407 bytes
  1 files changed, 0 insertions(+), 0 deletions(-)

http://github.com/horde/horde/commit/3e0131a16105d0e387d1369b2fcb1c0f3891174a

And highlighting the whole row on hover doesn't make any sense.   
Clicking on the row causes the message to be loaded, not for the 
checkbox to be selected.  (The checkbox will be selected when this 
occurs, but that is due to the semantics of displaying the message and 
not because a row click is designed to click the checkbox).

I could see using a slightly ghosted checkbox on hover.  In fact, I 
believe this is what we used in the past before the design makeover so 
this might be a regression.

Agree with Jan.  This change was made after input from a UI expert, 
and has been around for probably 7 years now, and we've never heard 
negative feedback before.

Having a hint such as highlighting the row (the most common method) is 
very useful.  Showing the checkmark before it is actually selected 
makes it look like it was selected.  If the click doesn't register, 
you cannot tell until the mouse pointer is moved off the checkbox.   
When deselecting a row, the click action is not visible because the 
box shows as being checked due to the mouse pointer is over not, and 
not because it is still selected.  Again, the actual state of the row 
cannot be determined until the mouse pointer is moved off the checkbox.

How is that confusing? It's a user hint that this is an active 
element, like links that change colors or underlined when hovered.

When selecting messages from the Webmail folder list, hovering the 
mouse pointer over a checkbox causes it to appear checked.  Even when 
deselecting a message, the checkbox does not disappear until the mouse 
pointer is moved away.  This behavior is confusing and 
counter-intuitive.