With Po4a 0.33.1 the following slightly annoying behavior is observed:
cat >test.xhtml <<'EOF'
<!--#include virtual="foo" -->
<title>Foo</title>
<p>Bar.</p>
<!--#include virtual="bar" -->
EOF
po4a-gettextize --format=xhtml -o ontagerror=silent \
--master test.xhtml --po test.pot
po4a-translate --keep=0 --format=xhtml --master test.xhtml \
--po test.pot --localized test.bg.xhtml
--- test.xhtml
+++ test.bg.xhtml
@@ -1,7 +1,9 @@
-<!--#include virtual="foo" -->
+
+<!--#include virtual="foo" -->
<title>Foo</title>
<p>Bar.</p>
+
<!--#include virtual="bar" -->
The extra line above the second directive and the stripped line after
the first directive are bearable (although in theory the two files
should be identical?) but the two blank lines at the beginning
definitely sound like a bug to me.