[weberer]

I'm a native English speaker and this trend confuses me pretty often. It's not always clear whether the person:

1. is sincerely asking a question

2. accidentally hit they question mark key instead of the period

3. is mimicking the valley girl inflection

It's not that much of a problem here, but it's much more pronounced in places where people rarely use complete sentences to begin with. Such as chat rooms, etc.

[reddit_clone]

> is mimicking the valley girl inflection

:-) I was thinking this but couldn't find the right phrase.

It could also be expressing uncertainty. You want to make an assertion but not 100% sure you are right. A question mark at the end expresses some self doubt and leaves it open to correction. I use '?' that way quite often.