extra hyphen in underscore hyphenation

[Pablo Rodriguez via ntg-context <ntg-context@ntg.nl>]

Dear list,

I have the following sample:

  \startluacode
  function document.addfunnyhyphen(tfmdata)
      local underscore = utf.byte("_")
      local char       = tfmdata.characters[underscore]
      if not char then return end
      tfmdata.characters[0xFE000]   = {
          width    = 0,
          height   = 0,
          depth    = 0,
          commands = {
              { "right", -char.width },
              { "down", char.depth },
              { "slot", 1, underscore },
          }
      }
  end

  utilities.sequencers.appendaction("aftercopyingcharacters",
  "after","document.addfunnyhyphen")
  \stopluacode

  \definehyphenationfeatures
     [underscore]
     [righthyphenchar="FE000]

  \sethyphenationfeatures[underscore]%
  \setuphyphenation[method=traditional]%

  \starttext
  \startTEXpage[offset=1em, width=4em]
    \hsize\zeropoint\tt
    \hyphenatedword{legibility-legible}
  \stopTEXpage
  \stoptext

In current latest (and in many versions before), I get an extra hyphen
in the next line after the hyphen, such as:

       ity-
       -leg

As far as I can remember, I would say this used to work before (no extra
hyphen was added in the next line.

What am I missing here?

Many thanks for your help,

Pablo
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