The watchfreaks post point out several common problems with the "Is this a Fake" type posts.
1) the level of fake is getting astonishingly good. There have been more than a few that required opening them up to make sure.
2) some brands, and Tissots in particular, make major AND minor changes on models seemingly at will. So a different color whatsis or wacky looking thingy may not indicate a fake. (Or then again, they may).
3) minor blemishes/ poorly finished areas on a moderately priced watch are not uncommon and are no indicator of a watch being a fake.
4) neophytes watch buyers (I do not mean to disparage them - only their experience) usually are overly concerned with insignificant details and underly concerned with the the most important detail - THE SELLER.
a) a top seller will never sell a fake. They are expert and have the advantage of actually holding the watch in their hand
b) low ranked sellers may intentionally sell a fake (you are screwed), might be unaware they are selling a fake (you might be screwed, might not. It varies)
or might sell a gennie watch (you score!)
Time after time we see 1st time posters ask if a watch is real only to go to the auction site (when they don't try and hide what they are doing so someone doesn't go and bid on it themselves - pleasssssse!)and discover that the seller has red flags out the kazoo.
Best technique I know of is to see if a watch looks fake "at a glance", if the pictures are of crappy quality pass on the watch, if not, glance at the sellers location and total transactions. More than 200 (ideally > 1000) and from a location not known for shady operators then open the feed back - look at the negatives. Still OK? Then open the positives. Read the description - if they guy comes across like a used car huckster ( "Never worn","Got as a gift" "My wife gave it to me and now we are divorced", "Found in my late father's belongings" and the number one tip off "I don't know anything about it") you may want to think long and hard about continuing. If he looks OK then scrutinize the watch pictures . If the watch looks ok then buy it. Notice that I actually spend as much or more time vetting the seller. The only way to do it.