The option to hide your timezone doesn’t make any sense if the message body also contains the real timezone.
The latter is controlled by the template. The easiest way to change it would be to just edit the template. If you want the setting to control the template also then the setting needs to be exposed in templates.
I have created a template. It seems to place two timezone offsets on the first line in my reply e-mail:
On {{.OriginalDate}}, {{index .OriginalFrom 0}} wrote: {{trimSignature .OriginalText | wrap 70 | quote}}
On 2024-09-08 01:05:45 -0700 -0700, "*****" <notifications@github.com> wrote:
This is on OpenBSD 7.6-beta and aerc 0.18.2.