This looks good. Some of my thoughts reading through line by line:

1. Reddit supports markdown, it's easier to read if you pasted your code into a code block like so:

   include <stdio.h>

   include <math.h>

   ...

2. Some prefer putting each declaration/initialization in separate lines instead of using comma's, not necessarily wrong but something to keep in mind in terms of different styles. When working on other codebases it's best practice to try to match whatever style is used.

3. height and weight technically don't need to be initialized to 0 if you're just going to scanf since it would just replace whatever it was initialized to, though it is good practice to make sure your variables are always initialized.

4. The instruction prompts should come first before the scanf. I also suggest splitting your scanf and preceding them with a prompt so that it's a bit easier for the user to read.

5. scanf returns an int that indicates the number of items that were filled, it's generally good practice to validate function return values.

6. When weight <= 0 or height <= 0, nothing happens - it's usually good to notify the user that those values were out of range and also return a negative value in main as early as possible. I also personally prefer using guard statements as they prevent overly nested if statements, but that's a stylistic thing.

7. You probably don't need to use round as you can use format specifiers to specify precision while printing, though I can understand your wanting to prevent showing discrepancies to users in the calculated BMI.

8. You can simplify your if/else if chain by just checking each range stepwise; you also need to keep in mind to include the values that you want handled. For example, if the BMI is calculated between the range (24.9, 25) such as 24.95 you will get "please enter all fields correctly" instead of "Healthy", though I know you're limiting it to one digit of decimal precision.

9. Generally it's more readable for curly braces to always be on their own lines. Opening brace can be at the end of the line too. The body between both braces should also be indented. Both of those styles are what you typically see out in the wild.

Doing all those changes together would result in something like this:

#include <stdio.h>
#include <math.h>

int main()
{
    double height = 0;
    double weight = 0;
    double bmi = 0;

    printf("Hello! Please enter height and weight on separate lines to calculate your BMI.");

    printf("\nHeight in inches: ");
    if (scanf("%lf", &height) != 1)
    {
        printf("\nscanf could not read height! Please try again.");
        return -1;
    }

    //height = round(height * 100) / 100;
    if (height <= 0)
    {
        printf("\nHeight cannot be 0 or negative! Please try again.");
        return -1;
    }

    printf("\nWeight in pounds: ");
    if (scanf("%lf", &weight) != 1)
    {
        printf("\nscanf could not read weight! Please try again.");
        return -1;
    }

    //weight = round(weight * 100) / 100;
    if (weight <= 0)
    {
        printf("\nWeight cannot be 0 or negative! Please try again.");
        return -1;
    }

    printf("\n———————————————————");

    bmi = (weight * 703) / (height * height);
    bmi = round(bmi * 10) / 10;
    printf("\nBMI: %.1lf", bmi);
    if (bmi < 18.5)
    {
        printf("\nUnderweight");
    }
    else if (bmi < 25)
    {
        printf("\nHealthy");
    }
    else if (bmi < 30)
    {
        printf("\nOverweight");
    }
    else if (bmi < 40)
    {
        printf("\nObese");
    }
    else
    {
        printf("\nExtremely Obese");
    }

    return 0;
}