The "official" FindAGrave guideline:

"Death certificates may be added via the "Add a photo" button on the memorial page. Please select the option for "Other" in the "Type of photo:" to be added, as it is not a Grave, Person or Family photograph. NOTE: Death certificates don't necessarily contain completely accurate information."

What are gravesite details?

These are details specific to the grave marker or site. Some examples of details like this are description, condition, history, significance of symbols, that the grave is unmarked, or known mistakes on the marker.

If burial information is unknown for an individual, Find A Grave is probably not the right place for their information. I do not link "Burial Unknown" memorials.

I will add military rank to those who were killed in action. Otherwise I generally do not add military rank to individuals buried in national cemeteries. - "In the democracy of the dead all men at last are equal. There is neither rank nor station nor prerogative in the republic of the grave." ~John J. Ingalls, 1889

The inscription field is to be used for words, phrases, or sentences found on the headstone other than the person’s name or birth and death dates. Find A Grave's definition of the inscription field. Please do not suggest otherwise.

The following statement was obtained from the profile page of Find A Grave contributor, Kathy S., #46944127. If I decline to change a person's name on their memorial it may be due to this:

"We respect the name the person chose to be buried under and will use the same for their memorial (which may also help prevent duplicates). If you have a different name, we are happy to add the source to the bio for you upon request."