May be that this long discussion suffers  a lack of communication?

2 languages were used both like English but one is the English of the developers the other that of artists/users...similar  words are used but seem  used with quite different meanings

to summarize  "use transparency as a colors"

  1
" brushing a transparent color" is exactly as use the eraser (if there is a alpha  channel) Maciej Pilichowski seems  agree on this point

2  SO what is missed  seems just a equivalent of "AIRbrushing a transparent color",,..a option in the eraser tool to use airbrush instead then a brush will solve that, and for sure will be a cool new feature.

3 May be is missed, also the possibility to select transparent area as was a color,meaning  using the magic wand or the color selector tool..

but since there is "alpha to selection"(=select transparency) that is no too missed... well is missed its usability since that option is hided in a weird place and has a cryptic name (all understand "transparency" less "alpha" ..more the Layer menu really do not seems most intuitive place to search function related to selections)

For usability may be good  add to the "select by color"  dialog a checkbox "select transparency",..that checkbox if checked will simply call  the good old "alpha to selection" function (this from a developer's point of view..from average user's point of view that will just "select the transparent color")

 to my logic "alpha to selection" may be well seen as a subset of "select by color" (in this case will be "select by absence of colors " that as concept seems strictly related )

i believe a "use airbrush" option for eraser tool and a "select transparency" checkbox added to " select by color" will be  both nice addition also for who is no much interested to " paint with transparent colors"

then a question for Maciej Pilichowski..i understand you well? a "airbrush-eraser" to allow to "airbrush transparent color" and a more intuitive place and name for "select transparency" will realize your wishes?

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