1) HTC could only block S-OFF by releasing a firmware update that patches the exploit used to gain S-OFF. Anyone who is not S-OFF already and updates, would not be able to use whatever method existed previously to S-OFF.
2) Hboot is technically just one file out of the firmware file package that makes up the bootloader screen and reports the firmware version number or hboot version number. This can get confusing because technically one could just flash or update an hboot, without updating the rest of the device firmware so, while the hboot version will show to be one version, the rest of the firmware files to match that hboot version may not actually be those pertaining to the hboot version projected. Hence, it is usually within best practice to update your hboot along with the rest of the firmware files that have been updated with that hboot version. It is common practice on XDA to refer to the entire group of firmware files from an hboot version as simply the hboot.
Typically updating one's hboot is done by flashing an HTC signed RUU or OTA. But can also be done by flashing the firmware.zip file contained within them respectively. It is important to note, if just flashing the firmware.zip files, they must be done sequentially or altered properly to contain all sequential updates otherwise one will brick and probably require JTAG.
3) After unlocking and modding my phone to my liking, I have not one complaint. This phone is everything I wanted in a phone when setting out to upgrade.
Sent from my HTC One_M8 using xda app-developers app
: Telus HTC One M8: 3.16 HBOOT S-OFF
Exad's m8 Everything Explained Thread