There was a discussion where the Brazilians explained it, but I can't for the life of me find it, as the search feature is still so limited. Basically, your answer should be accepted, but I understand why it wasn't. They rarely use "destas" (or maybe it's a regionalism...?). "Dessas" translates as both "these" and "those". In EP, however, that doesn't happen.
Well, it's a bit difficult for me to tell, since I can instantly detect mistakes in my native language, but can't nearly as well for even those with which I have some familiarity, like Italian. My impression is that Portuguese is the least polished one so far, even comparing to the other current Beta, Italian. So please bear in mind that this is rather subjective, also because I spend quite time in the Portuguese forum, and the more scarce input from natives for those other languages (also a feeling, I don't have any data to back that up) doesn't necessarily mean they're that far ahead. It could be that Portuguese people and Brazilians are more prone to invest in such corrections :-)
By the way, feel free to correct my English as well.
OK, here is a correction for your other comment on "Pertence".
"The downsides are definitions not being listed vertically and it also doesn't conjugate verbs."
"The downside is definitions not being listed vertically nor conjugated." like "nem"
"The downside is definitions not being listed vertically and not conjugated either." like "tampouco" and here you said what I believe would be the equivalent mistake in PT; "não ... tambem".