Thank you for contacting Syncfusion support.
We would like to let you know that if your requirement is about to single user reply and comment section, we recommend you to use the DataTemplateSelector in the SfListView instead of nested SfListView for better performance. Please refer the below documentation below.
If your requirement is about to multi user comment and reply section, then you can achieve the requirement through SfTreeView control with definite ItemHeight. Please refer the following UG documentation link.
Currently, SfTreeView does not have dynamic sizing support for its content. We have already logged a feature request for this requirement and added it into our feature request list.
You can now track the status of your request, review the proposed resolution timeline, and contact us for any further inquiries through this link.
Please let us know if you require further assistance.
Dinesh Babu Yadav