Is there already an approximate date when version 1.0.0 should be released?
In this version there should probably be an innovation that is fascinating, not only for me:
Comment Likes
Since at least 15 instances, including larger ones, have now switched to the development version and, if I’m not mistaken, this feature is also used there, I’m considering switching as well.
I usually just update to releases, but I am wondering if it might be worth making an exception this time.
No.
You are mistaken. Likes on comments might come back, and there is an open Pull Request for it, but it still has lots of work left to be done on that before it can be merged.
It may of course be the case that these are individual instance updates.
However, I have already read from other users that this should be possible on their instance, and at least on diaspora-fr.org, with the Code 1.0.0-dev version I could see that liking of comments is already possible.
Well this means that @flaburgan has merged this not-fully-reviewed and not-yet-finished PR to his pod and is running that. That’s fine and his decision. Fla knows what he’s doing since he’s an active contributor to the code - so he also knows that he has to fix issues himself if this causes issues (which it very well might, as it involves database changes).
Comments on Likes is not a feature that’s merged into any official project branch, and until the work on that feature is done, it’ll stay that way. If you decide to merge the PR into your own customized fork, you’re more than welcome to do so - but you will be on your own regardless of what happens.
Thank you for your prompt explanation 
I confirm that I integrated that out-of-tree patch manually and that it is not yet merged into the development branch.
To the best of my knowledge, it works without any problem.
Thanks for the answer.
As I noted, the last edit of the PR is from March this year.
So there’s a good chance that a merge won’t last too long. I’ll wait patiently for a while then