Is there any personal data saved inside a Blender file? If I upload a file with an HDRI-map, will the others see it? And will the name of the folder in which it lies be visible in the file? Will my computer name be visible? In general, what are the pitfalls about personal data when uploading blender files?
The path to the image will be visible even if packed. However if you used a subdirectory of the path of the .blend e.g. //Textures/ (// means dir of the .blend) only this will be visible, including the name of the image. The only way Blender uses absolute paths (to my knowledge) is when you import the image before saving the file, or if you told it that in the global settings.
Computer name etc. will not be visible, there is no username, registration or anything else. The version you used to last edit the file can be determined, eg. 2.83.
I am not aware of any (other) pitfalls.