Note that one of the posters you've been arguing with ("VZ"; argument here: https://news.ycombinator.com/item?id=24259040), turned out to be the WxWidgets maintainer. According to the comment though, mentioning this constitutes a cheap trick <rolling eyes>.

Regardless, there is a very interesting concept in the explanation: using native widgets through WxWidgets (and possibly, widget toolkits in general) requires following specific guidelines. Failing to do so will make the widgets look bad, even if they're native.

  First of all: The "VZ" who wrote in the thread you linked, is Vadim Zeitlin, the
   core maintainer of wxWidgets. His word is the highest authority in the wxWidget
  s world.
  
  My 2 cents:
  
      are all the widgets provided by WxWidgets native?
  
  No. But if a native implementation of a control exists on a specific platform, i
  t will be used (i can't think of any exceptions right now, but it's possible the
  re are a few).
  
  Most widgets are native on all platforms, e.g. wxButton, wxTextCtrl, etc.
  
  Then there are widgets that are only native on some platforms. E.g. wxDataViewCt
  rl. Is has native implementations on OSX and GTK, but as no such control exists 
  under Windows, a generic implementation is used there.
  
  Then there are widgets that have no native implementations at all, e.g. wxGrid.
  
  In general, wxWidgets just gives you the toolset to develop crossplatform GUIs. 
  That doesn't guarantee it that they'll look good everywhere out of the box. This
   also requires "good" behavior of the developer. E.g. they should not use absolu
  te values of controls sizes and positions, but use wxSizers (the wxWidgets layou
  t system) instead. Lately they must also be prepared for high-dpi screens, good 
  support for that is only available in wxWidgets for a few weeks now.
  
  Also, many open source developers only develop on one platform and hardly ever o
  r never test on other platforms. Often they just don't want to invest more time 
  to make their application look good everywhere.
  
  Regarding https://imgur.com/LjDhPOv
  
  wxHexEditor uses wxAUI, this is not native anywhere. The window with the hexdisp
  lay could be custom drawn, there is no control that does this out of the box. Or
   it might be a wxGrid, hard to say.
  
  wxMP3gain looks fine to me
  
  easyMP3Gain seems to be one of the case where the developer just didn't care to 
  make it look good.