[ticmasta]

Well, if they're trying to get you to switch or to adopt something new, they're trying to sell. There's more to trading than just money for product/service; could be attention, effort, endorsement, opinion and other signalling factors, etc.

[yaroslavm]

By your definition, technically, any piece of content on the Web should be considered a sales page—including your comment, where you'se selling your opinion or attention. If that's the case, does it really make sense to label something a "sales page" in a negative way?

Is there any other way to present a new FOSS project besides telling about the upsides? Trashtalk it from the start, maybe? I don't really get it.

[fhbdukfrh]

Yep, that's kind of the point of upvotes or karma: You present your content and try to get people to buy it. Not sure where you get the negative sales page aspect though. I made no judgement on the presentation technique or quality, just that open source or not, they are still selling something.