Unicode "no-op" Character?

[Shawn Steele via Unicode]

+ the list.  For some reason the list's reply header is confusing.

From: Shawn Steele
Sent: Saturday, June 22, 2019 4:55 PM
To: Sławomir Osipiuk <sosipiuk at gmail.com>
Subject: RE: Unicode "no-op" Character?

The original comment about putting it between the base character and the combining diacritic seems peculiar.  I'm having a hard time visualizing how that kind of markup could be interesting?

From: Unicode <unicode-bounces at unicode.org<mailto:unicode-bounces at unicode.org>> On Behalf Of Slawomir Osipiuk via Unicode
Sent: Saturday, June 22, 2019 2:02 PM
To: unicode at unicode.org<mailto:unicode at unicode.org>
Subject: RE: Unicode "no-op" Character?

I see there is no such character, which I pretty much expected after Google didn't help.

The original problem I had was solved long ago but the recent article about watermarking reminded me of it, and my question was mostly out of curiosity. The task wasn't, strictly speaking, about "padding", but about marking - injecting "flag" characters at arbitrary points in a string without affecting the resulting visible text. I think we ended up using ESC, which is a dumb choice in retrospect, though the whole approach was a bit of a hack anyway and the process it was for isn't being used anymore.
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