Thunderbird doesn't remove the signature in a reply

Neither plain-text nor HTML-signatures are being removed in replies, even though they are at the bottom of the email i'm replying to, prepended by the default -- tag on a dedicated line, as is the standard. I double checked that mail.strip_sig_on_reply is set to true. This happens on two separate accounts configured on my client. Thunderbird Version 140.6.0esr on Tuxedo OS (equivalent to Ubuntu 24.04)