There are a number of possibilities.
It may be that the way you have provided the space for your forum, within Blogspot fixes the space available for your Nabble forum. While short pages will display in full, long ones will not and show ythe "View more..." prompts you describe. In this case you need help from Blogspot to make the area expand as required.
It may be that a slow connection speed and a long Nabble page, means that Blogspot has to re-assess the space it has allowed for the forum. That can lead to delays in re-configuring the size of the space allowed for the forum, which then show "View more"... prompts until the new size is calculated.
If your users are responding via email, it is very common for people to "top post" replies above the quotes of earlier replies. In that case Nabble will cut short the quotes with a message that toggles between "[show rest of quote]/[hide part of quote]. Is that what you are seeing
The "Edit This Page" function is a major feature of Nabble. It allows you, to examine how other forum administrators have customised their forum and as a Forum Administrator yourself to edit the code that runs your forum to produce almost limitless customisation.
Volunteer Helper - but recommending that users move off the platform!
Once the admin for GregHelp now deleted.