Currently, export of comments through OCS is not done quite right, and subcomments lack their <comment></comment> wrap tag. An example of the issue can be seen here, and looks as below:
<ocs> <meta> <status>ok</status> <statuscode>100</statuscode> <message/> </meta> <data> <comment> <id>1470458</id> <subject/> <text> +Wonderful! Love the Green focus color! Thank you so much! </text> <childcount>1</childcount> <user>Trinity</user> <date>2019-04-21T16:54:21+00:00</date> <score>0</score> <children> <id>1470485</id> <subject/> <text>Thank You, Trinity!</text> <childcount>0</childcount> <user>l4k1</user> <date>2019-04-22T02:46:35+00:00</date> <score>0</score> </children> </comment> <comment> <id>1470405</id> <subject/> <text>+</text> <childcount>1</childcount> <user>charlie-henson</user> <date>2019-04-21T01:34:10+00:00</date> <score>0</score> <children> <id>1470411</id> <subject/> <text>Thank You, Charlie! </text> <childcount>0</childcount> <user>l4k1</user> <date>2019-04-21T02:13:02+00:00</date> <score>0</score> </children> </comment> <comment> <id>1470360</id> <subject/> <text>+</text> <childcount>1</childcount> <user>qajqii</user> <date>2019-04-20T09:59:55+00:00</date> <score>0</score> <children> <id>1470363</id> <subject/> <text>Thank You, qajqii !</text> <childcount>0</childcount> <user>l4k1</user> <date>2019-04-20T11:36:30+00:00</date> <score>0</score> </children> </comment> </data> </ocs>
As visible above, the children are simply output in a <children> tag, which will fail to be read by e.g. Attica, which expects each child to be a fully formed comment.
(also sorry for not opening an actual task and just sending you a message about it, this should be a bit easier to track, i hope ;) )