1) Forget about comment #7; as I already thought this seems to be a misfeature in Metacity: Bug #379242. Though, if there is another solution that does not have this issue, you can update the patch.

2) As you said by im, I did omit this part of the patch:

+ if ([winfo exists $priv(wpageversion).l0]) {
+ return
+ }

...to fix this error:

can't read "priv(wpageversion)": no such element in array
can't read "priv(wpageversion)": no such element in array
while executing
"winfo exists $priv(wpageversion).l0"
(procedure "::UserInfo::VersionCB" line 7)
invoked from within
"::UserInfo::VersionCB ::UserInfo::ladybugjabberse ::jlib::jlib1 error {service-unavailable {The server or recipient does not currently provide the req..."
("uplevel" body line 1)
invoked from within
"uplevel #0 $cmd [list $jlibname $type $subiq]"
(procedure
<snip>

*However*, a new error appears:

window name "l0" already exists in parent
window name "l0" already exists in parent
    while executing
"ttk::label $f.l$i -text $key:  -wraplength 300 -justify left"
    (procedure "::UserInfo::VersionCB" line 37)
    invoked from within
"::UserInfo::VersionCB ::UserInfo::ladybugjabberse ::jlib::jlib1 result {query {xmlns jabber:iq:version} 0 {} {{name {} 0 Coccinella {}} {version {} 0 ..."
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 $cmd [list $jlibname $type $subiq]"
    (procedure "::jlib::invoke_iq_callback" line 5)
    invoked from within
"::jlib::invoke_iq_callback ::jlib::jlib1 {::UserInfo::VersionCB ::UserInfo::ladybugjabberse} result {query {xmlns jabber:iq:version} 0 {} {{name {} 0 ..."
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 $iqcmd($id) [list result $subiq]"
    (procedure "iq_handler" line 67)
    invoked from within
"iq_handler $jlibname $xmldata"
    (procedure "::jlib::dispatcher" line 9)
    invoked from within
"::jlib::dispatcher ::jlib::jlib1 {iq {from <email address hidden>/Coccinella@sander-laptop id 1022 xml:lang en type result to <email address hidden>/Coccinella@..."
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 $wrapper($id,parsecmd) [list $wrapper($id,tree,2)]"
    (procedure "::wrapper::elementend" line 41)
    invoked from within
"::wrapper::elementend wrap1 iq -namespace jabber:iq:version"
    ("uplevel" body line 1)
    invoked from within
"uplevel #0 $options(-elementendcommand) [list $tag] $empty $ns"
    invoked from within
"ParseEvent:ElementClose $tag [array get options]"
    invoked from within
"::sgml::parseEvent {{} {} {} {} iq {} { <email address hidden>/Coccinella@sander-laptop' <email address hidden>/Coccinella@sander-laptop' xml:lang='en..."
    ("eval" body line 1)
    invoked from within
"eval ::sgml::parseEvent [list $tokenised] $parseOptions"
    (procedure "parse" line 60)
    invoked from within
"parse xmlparser2 {<iq <email address hidden>/Coccinella@sander-laptop' <email address hidden>/Coccinella@sander-laptop' xml:lang='en' type='result' id..."
    (in namespace inscope "::xml::tclparser" script line 1)
    invoked from within
"::namespace inscope ::xml::tclparser parse xmlparser2 {<iq <email address hidden>/Coccinella@sander-laptop' <email address hidden>/Coccinella@sander-l..."
    ("eval" body line 1)
    invoked from within
"eval $classinfo(-parsecommand) [list $name] $args"
    (procedure "::xml::ParserCmd" line 46)
    invoked from within
"::xml::ParserCmd xmlparser2 parse {<iq <email address hidden>/Coccinella@sander-laptop' <email address hidden>/Coccinella@sander-laptop' xml:lang='en'..."
    ("eval" body line 1)
    invoked from within
"eval ::xml::ParserCmd xmlparser2 [list $method] $args"
    (procedure "xmlparser2" line 1)
    invoked from within
"$p parse $xml"
    (procedure "parsereentrant" line 10)
    invoked from within
"parsereentrant $id $xml"
    (procedure "wrapper::parse" line 6)
    invoked from within
"wrapper::parse $lib(wrap) $data"
    (procedure "::jlib::recvsocket" line 24)
    invoked from within
"::jlib::recvsocket ::jlib::jlib1"

Can you take a look at this?

3) Maybe it is a good idea to add similar code to the History, Edit Contact, and Contact Actions dialogs.