This puts quoted text in a collapsed TitleBox. This reduces vertical scrolling. Edit the local copy of html/Ticket/Elements/ShowMessageStanza.

# diff /usr/share/request-tracker3.8/html/Ticket/Elements/ShowMessageStanza ShowMessageStanza
50c50
<     $m->out('<pre>') if $plain_text_pre && !$Depth && !$plain_text_mono;
---
>
51a52
>     $m->out('<pre>') if $plain_text_pre && !$Depth && !$plain_text_mono;
58a60,61
>
>
63a67
>
66a71
>
67a73,87
>         # don't include the TitleBox in the pre-tag
>         # Add titlebar if this is the first nested message (Depth == 1)
>         if ( $Depth == 1 && $First ) {
>             $m->out('</pre>') if $plain_text_pre && !$plain_text_mono;
>             $m->out('</div>');
>             $m->comp( '/Widgets/TitleBoxStart',
>                        title    => loc('Expand transaction history'),
>                        class    => 'transaction-history',
>                        bodyclass=>'hidden',
>                        class    =>'rolled-up',
>             );
>             $First = 0;
>         }
>         $m->out( qq{<div class="message-stanza-depth-$Depth } .($plain_text_mono ? "plain-text-white-space" : "").qq{" style="color:$colors[$Depth]">});
>         $m->out('<pre>') if $plain_text_pre && !$plain_text_mono;
70c90
<         $m->out( qq{<div class="message-stanza-depth-$Depth">} );
---
>
78a99
>         $m->out('</pre>') if $plain_text_pre && !$plain_text_mono;
79a101,108
>         # Close TitleBox if we're at the end of the last nested message
>         if ($Depth == 0 && !$First ) {
>             $m->comp('/Widgets/TitleBoxEnd');
>             $First = 1;
> ##
>             $m->out( qq{<div class="message-stanza-depth-0 } .($plain_text_mono ? "plain-text-white-space" : "").qq{">});
>             $m->out('<pre>') if $plain_text_pre && !$plain_text_mono;
>         }
83d111
<     $m->out('</div>');
84a113,115
>     $m->out('</div>');
>
>
105a137,138
>
> my @colors = ('#000000', '#660000', '#006600', '#000066', '#cc0000', '#00cc00', '#0000cc', '#ff0000', '#00ff00', '#0000ff');
108,110c141,145
< $Message => undef
< $Depth => 0
< $Transaction => undef
---
> $Message      => undef
> $Depth                => 0
> $Transaction  => undef
> $First                => 1
> $Last           => 0