I think those threads should be banned. Often, it's people desperately trying to conceive, and, as you say, posters give them false hope by telling them 'YES!! I can see a line, congratulations!' I also think pregnancy testing kits should come with advice telling people not to test until their period is at least one week overdue. Sensitive pregnancy tests pick up chemical pregnancies, which again gives false hope - and also grief at the pregnancy loss when menstruation arrives bang on time.
What do you all think about the rash of threads recently, where the poster has either felt something move in her stomach, or leaked colostrum, and subsequently finds out they are 30+ weeks pregnant? There were at least 4 separate threads by different posters, over the last few months.