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I assume that my posts are deleted when I delete my Facebook account, but what about the "like"s that I gave to other posts? Is the "likes" count on that post/page reduced?
Or the comments I made on other posts? Are they deleted?
And what happens to the conversations I had in chat?
Do they still appear to the people I chatted with?
Are you referring to your News Feed (Top News), News Feed (Most Recent), or the Recent Activity on your profile?
I think that News Feed (Top News) only displays what Facebook considers to be most interesting to you, so I wouldn't expect your own likes/comments there. The News Feed setting that you mentioned applies to the Most Recent setting.
News Feed (Most Recent) does not display individual stories for comments and likes on posts; you would only see them under the corresponding post, if it is expanded. Are you saying that you expanded the likes/comments and you can see comments from other people but your comment is not there? Sometimes it takes some time for it to show up although it shouldn't take days (unless it was deleted).
If you are referring to the Recent Activity on your profile, there is an additional setting for that that you didn't mention. On your profile's Wall (not your News Feed), scroll to the bottom and click Edit Options. If you have hidden any kinds of stories from your Recent Activity these will be listed and you can unhide any of them by clicking the X and then Save.
As for the Photos tab, that used to be a known issue although the link to Facebook Help in that answer does not seem to work now. I don't know if that means that it should be fixed.
I don't think G+ (or any other) will delete your content.
I think there is a best practice somewhere that says "do not delete anything" (at least this is how I learned database design), it's just like in nature "nothing is lost, everithing is recycled". :)
They rely on content—think of Google search—sometimes it seems that it knows what you want to search, beacause the more users search, their database grows bigger and bigger, the more database searches that can compare with the more precise is the result. This is true for social media to, they build a profile for every user, and they build the so called "social graph" of the world (read this interview). :)
What they do with the results... first they are showing custom ads, I think they even sale the results to big companies—they have data that is extremly valuable in marketing. For example: a phone company launches 2 new models, m1 and m2, after a few weeks they go to G+, Facebook, and ask them, what is the phone that users talk more m1 or m2, and what phone from a competitor is on top of users talks?
So you need to know that every time you register to a service like this, ALL your data will be stored forever by the company, be it G+, Facebook... you name it.
That's my opinion.
Best Answer
You actually deactivate it, and once you do that all your comments, likes, shares, post and everything associated with your profile disappears like it never existed. But your message conversation will still be visible on your friend's inbox just there won't be your profile picture and link to it.
If you reactivate the account in future all your likes, comments etc. will reappear.
Update: If you choose to permanently delete your Facebook profile, the same thing happens plus all your data from facebook servers will be erased permanently, so there's no way you can regain access to your account as well as the data associated with it.
If you want you can download all your data from Facebook before deleting the account. Goto your account settings https://www.facebook.com/settings and click on the link that says "Download a copy of your Facebook data" and download the archive.