One of my patches for this feature introduced a corner-case regression
involving the option `erc-echo-timestamps'. If `cursor-sensor-mode' is
somehow enabled outside of this module, then timestamps will still be
echoed even when `erc-echo-timestamps' is nil.

  commit ad3dc74e074719a58226e23a45c4556cd54c0a48
  Author: F. Jason Park <jp@neverwas.me>
  Date:   Wed Nov 24 03:10:20 2021 -0800
  
      Expose insertion time as text prop in erc-stamp
      
      * lisp/erc/erc-stamp.el (erc-add-timestamp): Add new text property
      [...]
      (erc-echo-timestamp): Make interactive and show timestamps even when
      the variable `erc-echo-timestamps' is nil.
      (erc--echo-ts-csf): Add new function to serve as value of
      cursor-sensor function text properties.
      * test/lisp/erc/erc-stamp-tests.el: New file.  (Bug#60936.)
  
   lisp/erc/erc-stamp.el            |  15 ++-
   test/lisp/erc/erc-stamp-tests.el | 207 +++++++++++++++++++++++++++++++++++++++
   2 files changed, 217 insertions(+), 5 deletions(-)

In addition to addressing the above, the attached patch includes a new
optional parameter for the command `erc-echo-timestamp'. It allows for
specifying a timezone for the echoed stamp via prefix argument or a new
option, `erc-echo-timestamp-zone'.

These changes are intended for ERC 5.6.