I am compiling the comments in the other bug here as well as some points made in IRC:

The commit https://git.gnome.org/browse/gtk+/commit/?id=b2e666bf8f297eb998331fa8ce0062ce7a5198fa makes impossible to disable blinking, which introduces a11y issues to people with high sensibility to blinking objects.

In spite that good defaults are desired, other systems have documented that software blinking can cause seizure.  Therefore, it is necessary to add the possibility to change the setting.

For reference, here is what other systems say:

From Microsoft A11y Tools:

   http://citrixblogger.org/2008/02/08/cursor-blinking/

    "
    Microsoft recommends turning off the cursor blinking to avoid seizure.

    Cursor Blink-Rate Options

    Users who have seizures might be sensitive to the blink rate of screen
    images, such as the cursor. You can use the Keyboard option in Control
    Panel to adjust the rate at which the cursor blinks, or you can prevent
    it from blinking at all. On the Speed tab, move the Cursor blink rate
    slider all the way to the left to prevent the cursor from blinking.
"

See section "Options for Users Who Experience Seizures" in
http://technet.microsoft.com/en-us/library/bb457128.aspx 


In IBM's "Human Ability and Accessibility Center" I found the following
recommendation for blinking objects:

    "Do not use flashing or blinking text, objects, or other
     elements having a flash or blink frequency greater than
     2 Hz and lower than 55 Hz.

     Rationale

     The purpose of this checkpoint is to ensure the software is
     developed so that it does not induce seizures due to the use
     of blinking or flashing.

     Text and objects that blink or flash can cause photosensitive
     epileptic seizures in susceptible individuals, particularly if
     the flash has a high intensity and is in the frequency range
     between 2 Hz and 55 Hz. This includes flashing text, turning
     graphics on and off or repeatedly changing between different
     images on the screen.
    "

It has some examples and test techniques that people might want to
check:

http://www-03.ibm.com/able/guidelines/software/swblinking.html


Finally, another reason cited as well is performance when running an
application over a network:

    In a Terminal Services environment (including Citrix), the cursor
    blinking can actually be a drain on the system and network.

http://citrixblogger.org/2008/02/08/cursor-blinking/

The subject is misleading - the cursor _will_ stop blinking after a few seconds. What you are complaining about is that you can't ensure that the cursor _never_ blinks, correct ?

First, I didn't know that the cursor would stop blinking after a few seconds of inactivity. If I did want a blinking cursor that's the opposite of how I'd want it, since a blinking cursor is used to attract attention, so you can find it quickly after a period of inactivity.

Second, you're right, I don't want it to blink at all. Or rather, I need it not to blink at all, especially the "block" style of cursor e.g. in gnome-terminal.

Thanks for the additional information.