I think in many cases this issue is hardware related; echo cancellation, VAD (Voice Audio Detection).

Depending on which ATA/analog phone combination or SIP phone your are using you may or may not have problems.

IMHO, the best solution for VoIP telephony is a true internet phone that plugs into ethernet. Note that wifi phones (or your Android or iPhone) can have this capability.

In short, I think this problem is up to the user to solve with the correct hardware. However, as VoIPo concentrates on ATA and not BYOD (understandable for the support issues), one is likely to experience these problems, and VoIPo is contributing by steering users torwards ATA and analog phones, which are more likely to have echo/'half-duplex' issues.

Here is a link to a review of a quality DECT IP phone. One could install this phone, using DECT cordless and a direct internet connection, without rewiring ethernet throughout their house. VoIPo does allow BYOD connections (that is all I use), but does not provide tech support for the device you choose.