A 200 response doesn't guarantee that your payload will actually contain any data. It depends on the server. The server might determine to respond with a 200 code but still not return any JSON code for your request.

I am not at all sure, but the server may be rejecting your request because it doesn't like your user agent. I have seen my own ESP8266 supply ESP8266HTTPClient as it's user agent for HTTP requests. You can see from the source code of the HttpClient class that this is the default:

HTTPClient::HTTPClient()
    : _client(nullptr), _userAgent(F("ESP8266HTTPClient"))
{
// etc...
}

You might consider setting the user agent for your http client object:

http.setUserAgent("Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0");

Alternatively, you might use curl to emulate the http request being formulated by your ESP device:

curl -vA "ESP8266HTTPClient" http://jsonplaceholder.typicode.com/comments?id=10

On my linux machine, this returns all the HTTP header information, followed by some JSON for the url you've specified in your code:

[
  {
    "postId": 2,
    "id": 10,
    "name": "eaque et deleniti atque tenetur ut quo ut",
    "email": "Carmen_Keeling@caroline.name",
    "body": "voluptate iusto quis nobis reprehenderit ipsum amet nulla\nquia quas dolores velit et non\naut quia necessitatibus\nnostrum quaerat nulla et accusamus nisi facilis"
  }
]

Maybe try that with the other url and see what comes out?

You might also modify your post with the Serial output of your sketch to provide more detail.

A 200 response doesn't guarantee that your payload will actually contain any data. It depends on the server. The server might determine to respond with a 200 code but still not return any JSON code for your request.

I am not at all sure, but the server may be rejecting your request because it doesn't like your user agent. I have seen my own ESP8266 supply ESP8266HTTPClient as its user agent for HTTP requests. You can see from the source code of the HttpClient class that this is the default:

HTTPClient::HTTPClient()
    : _client(nullptr), _userAgent(F("ESP8266HTTPClient"))
{
// etc...
}

You might consider setting the user agent for your http client object:

http.setUserAgent("Mozilla/5.0 (X11; Ubuntu; Linux x86_64; rv:78.0) Gecko/20100101 Firefox/78.0");

If you'd like to investigate a bit more, you might use curl from the command line (this works on linux) to emulate the http request being formulated by your ESP device:

curl -vA "ESP8266HTTPClient" http://jsonplaceholder.typicode.com/comments?id=10

On my linux machine, this returns all the HTTP header information, followed by some JSON for the url you've specified in your code:

[
  {
    "postId": 2,
    "id": 10,
    "name": "eaque et deleniti atque tenetur ut quo ut",
    "email": "REDACTED@EXAMPLE.COM",
    "body": "voluptate iusto quis nobis reprehenderit ipsum amet nulla\nquia quas dolores velit et non\naut quia necessitatibus\nnostrum quaerat nulla et accusamus nisi facilis"
  }
]

Maybe try that with the other url and see what comes out?

You might also modify your post with the Serial output of your sketch to provide more detail.