Use |ISO-8601| compatible date format:
let g:git_messenger_date_format = '%FT%T'
Don’t automatically close window:
let g:git_messenger_close_on_cursor_moved = v:false
Use scrollwheel, or emulated key, to move through history in window:
augroup jnrowe_git_messenger
autocmd!
autocmd FileType gitmessengerpopup
\ nmap <buffer> <ScrollWheelDown> o <Bar>
\ nmap <buffer> <ScrollWheelUp> O
augroup END
.. spelling::
scrollwheel