A minhag that I'd never seen before

[rhu]

This morning, someone came to me at shul
And pointed to the luach (calendar)
which said that there are those whose practice is
to keep wearing tefillin on this day
until the Torah reading has been done.
(Some background: on the middle paschal days
some people don't put tfillin on at all,
while others wear them until kedushah.
I'm in the latter camp.) It seems, said he,
that on the first day of chol ha-mo'ed,
we read the text kol peter rechem li
which is one of the passages contained
in the tefillin; therefore, there are some
who do not doff them before Hallel's sung,
but keep them on at least through revi'i.
I'd never heard of that before today,
And now I'm curious how widespread 'tis.
Do any of you know whence it arose?
(When Ezras Torah says yesh nohagim
I like to learn more ere I change my ways.)

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It's after dark, so sfirah's count's now three