The comparators don't emit light when powered by lamp, unlike repeaters.
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Kumasasa, these are two different bugs: that bug is about the front torch when it is toggled, while this is about the rear torches which occur when the comparator receives power.
In fact, this bug has an interesting trait: give yourself 149 and 150, and place both. Both are comparators, but 150 emits light and has its rear torches on. If 150 loses power, it becomes an ordinary comparator. It seems the game is not using 150 for the lit state, despite its existence.
In fact, 150 has a unique graphic as opposed to 149, which merely has the ordinary comparator graphic with lit torches. So, even if the lighting is intentional to reduce lighting updates, it does not seem intentional to leave one of the comparator textures unused, after updating its appearance.

@Gerrard Lukacs: You're right.
Reopened.
Duplicate of MC-8784.
Tails, as that bug makes no mention of light levels (only textures), perhaps edit it to include info about light, if you're closing this?
I was the first to point it out in MC-8784...
Well, I'm just saying it may be a good idea to add relevant info like that to the bug's title or description. A search for "comparators don't emit light" did not bring up that thread; it seems the comments aren't indexed for searches here (hence, if the report we're on right now did not exist, I would be the one posting a duplicate, as I would not have seen that thread even though I used the search function). Also, it would probably be more helpful for Mojang if the most pertinent info about a bug existed in the ticket itself, rather than down in the comments.
Duplicate of MC-6113, please use thesearch functionto see if your bug has already been submitted. Currentlyover 51%of tickets are being closed as duplicate.