You are hung up on this phrase.
Let's define a trade or service mark:
A word, symbol, or device (graphic) used on or in connection with goods or services in commerce as a distinctive indicator of the source or origin of those goods or services.
Let's break it down:
1. A word symbol or device. That should be pretty simple.
2. Used on or in connection with goods or services - the mark is located on the goods, like a label, or the service is advertised as being "Jim-Bob's Tax Preparation Service" on a sign or advertisement of some kind.
3. In commerce. That is the mark is on the goods or services in such a way that someone in a position to purchase them can see that they are so marked.
4. As a distinctive indicator. Anyone can put "beer" on a bottle of beer. That's what beer is. So the word "beer" is not distinctive. The word "Heineken" on a bottle of beer is distinctive. There is a relative scale of how distinctive a mark might be. Some things are generic, like "beer". Some things are descriptive, like "light beer". Some things are geographically descriptive like, "German beer". The line between "generic" and "descriptive" is an important one, since even "descriptive" marks may become distinctive through longstanding, continuous, and substantially exclusive use. "Philadelphia" is a mark owned by Kraft for cream cheese. "New York Pizza" is a geographically descriptive term used by a lot of people. At the high end of the scale are fanciful marks - marks which do not mean anything at all, like "Xerox", "Exxon" and so forth. In the middle range are arbitrary marks - marks which do mean something, but have no connection to the thing identified. These are things like "Delta" for faucets, or "Delta" for an airline. Note that the same arbitrary mark can be used for different things, like faucets and airlines, by different people. Between "descriptive" and "arbitrary", there is a category of "suggestive" - i.e. the mark is 'kinda, sorta' descriptive, but some kind of mental act of inference is needed in order to get from the mark to the product, like "Tidy Bowl" for a toilet bowl cleaner. Using "Tidy Bowl" may get you a tidy bowl, but the product is neither tidy nor a bowl. My favorite is "Invisible Fence" for a radio dog containment system. It is not invisible, and it is not a fence.
5. Of the source or origin. You might not know WHO makes the product or provides the service, but the mark serves as an indicator that "this stuff" is the "same stuff" that you bought last time by whomever makes it. "Budweiser" beer comes from whomever makes "Budweiser" beer, regardless of whether you have ever heard of Anheuser Busch.
Whether a domain name is being used as a trademark depends primarily on whether it is - displayed on or in connection with goods or services (which can include advertising services) and distinctive of the goods or services for which it is used, If it is merely used as an address, and not as a mark, then you haven't gotten near the "date in commerce" issue. So, if I have orangutan.com, and it is the URL for a PPC page advertising supplies for keeping orangutans, then we're not even going to bother with the date issue because it is a merely descriptive identification of the subject matter to which the use of the domain name relates. If I have orangutan.com, and have a PPC page for clothing at a webpage that says "Welcome to Orangutan.com, a directory of fine clothing", then I am using a distinctive indicator of the advertising services which I am providing to clothing vendors.
The bottom line is that your question - (a) has no general answer, and (b) probably doesn't get you any closer to solving your riddle than the other thread.