No, this is an unreversable action for that game once you disable the chat in that game.
disable chat

If you disable game chat, its because you don't want to chat to your opponent.
In live chess, if you disable game chat in the settings page, you can re-enable it again from there.
Otherwise game chat won't be re-enabled until the next game (in live chess).
Disabling game chat in the game is only applicable to that game.
Disabling game chat from live chess settings page is applicable for all live chess games.

kohai, you state that "In live chess, if you disable game chat in the settings page, you can re-enable it again from there." Let's say that you do this, you disable chat in the live chess settings page for what ever reason, and for some reason you decide that you want to say something to the opposing player while playing. In order to do so you would have to disconnect from the game for the settings to take effect. Correct me if I am wrong, but wouldn't it be easier to enable chat from the live chess game page? I am sure that there is a reason why this is not an option, but I thought it might be a suggestion worth mentioning to you.

If you turn off chat from the settings page, play a game, then during that game you go into settings, and re-enable game chat it won't take effect until the next game.

Why would you enable chat once you turned it off for a game? Are you talking about the same game? Why would you change your mind in the same game?
Off the top of my head I can think of a couple reasons why I would want to enable chat in live chess once it is disabled. Most people say good game (gg) or good move, etc. Maybe they changed their mind and want to say something. What if someone wants to compliment their opponent on a good move, but they can't because they clicked on the disable chat option?
A while back I clicked on the disable chat option for no specific reason, and there was no option to re-enable chat. It's not that big of a deal really. It's just kind of odd not to have the option to enable chat if there is an option to disable.
Why would you enable chat once you turned it off for a game? Are you talking about the same game? Why would you change your mind in the same game?
Off the top of my head I can think of a couple reasons why I would want to enable chat in live chess once it is disabled. Most people say good game (gg) or good move, etc. Maybe they changed their mind and want to say something. What if someone wants to compliment their opponent on a good move, but they can't because they clicked on the disable chat option?
A while back I clicked on the disable chat option for no specific reason, and there was no option to re-enable chat. It's not that big of a deal really. It's just kind of odd not to have the option to enable chat if there is an option to disable.

If you don't have enough vertical space for the chat, you won't be able to see it.
How many toolbars does your browser have? (top and bottom). Try using F11 on your keyboard.
Interesting topic. My policy has been to leave the chat feature turned on 99.99 % of the time. Once in a while you get someone who just will not quit yakking ( their plan is to try to distract other player ? ) or the odd person who may get nasty and there I've had to disable chat. In any of those cases I would certainly not wish to turn the chat feature back on. The way that I use chat I'm quite happy with the way this feature works
Is there a way to enable chat once it it disabled?