What to do: Install extension tbkeys-lite (https://addons.thunderbird.net/thunderbird/downloads/latest/tbkeys-lite/addon-987885-latest.xpi?src=search) and configure Preferences in Main key bindings as follows:
{
"0": "unset",
"j": "unset",
"k": "unset",
"o": "unset",
"f": "unset",
"n": "unset",
"r": "unset",
"a": "unset",
"x": "unset",
"c": "unset",
"u": "unset",
"b": "unset",
"m": "unset",
"p": "unset",
"s": "unset",
"t": "unset",
"w": "unset",
"]": "unset",
"[": "unset"
}
Why? Thunderbird by default has certain single key bindings which can cause unwanted destructive actions (e.g. archive an email thread), for example if a user wants to search for a string and the cursor is not or no longer in the quick search bar.
Affected version(s): All recent, e.g. 78.4.0
Solution in: https://bugzilla.mozilla.org/show_bug.cgi?id=615957#c78
Sample search engine search texts for displaying related bugs: thunderbird bug "disable single-key shortcuts"