I have just on a whim installed whatsapp for bluestacks on my PC, using my landline number, and so far I have made an interesting observation:

Right now Mitakuuluu works perfectly, everything as it should, messages get transfered instantly. However one small, interesting thing: At first my PC showed Mitakuuluu correctly as online and Mitakuuluu showed my PC as online when I had Whatsapp open. However now (a few hours later) I can still write and it works perfectly, but the PC shows Mitakuuluu as offline (last seen about an hour ago. I have "always show online selected".) and Mitakuuluu also shows the PC as not online, even when receiving messages.

Might be something on the whatsapp server side, perhaps?

(If you remember, I had made this observation before with a friend's messages, but in this case I controll the "other side" and there is definitively no "hide online presence" selected on either side.)

Edit: When I disconnect and re-connect Mitakuuluu, the status is shown correctly again as "online".