I hate to disagree with everything you just said, but I'm afraid I'm going to have to, seeing as its all basically wrong from what I can see in this case. There is indeed differing behavior per tab in this particular file, and no, the tabs are neither consistent in their number of spaces, nor are they the same as tabs inserted into the editor with the TAB key. I know, because I have tested it, and my experiences don't agree with what you just said. To prove it, I have attached the file we're all talking about here with said tabs, and you can look for yourself if you want to. Line 656 has a tab character that was copied/pasted from an online source into the editor and saved to file, between the "Media type" and "Subtype columns". That tab has a size of 3 space in length, I believe, and tabs later on in the file have varying lengths. Two more I checked were 5 and 4. As noted before, the default setting of gedit on my computer has a tab size of 8 spaces, and inserts tab characters into the file, and I am still using this default setting, so when I insert a tab with the TAB key in my editor, it creates a tab with 8 spaces (I know, because I have checked).
Note that I am using the gedit editor (version 2.30.3) in Ubuntu 10.04. Perhaps you would have different results if viewing the file in a different editor or different OS, I don't know. I'm just speaking about my own observations.
EDIT: And I just checked the file again, and found two more tabs with different lengths. One was 7 spaces long, and another one was 6 spaces long. Now chew on that one for a minute or two...