after upgrading from core 141 to core 144 my /boot partition is full (0% free). It was 8% free before the update. Is there something i can delete on /boot?
Your best option is to go to x86_64 version, if your hardware supports it, for the now necessary reinstallation. Separate PAE kernels are not used there.
If you need to stay with i586, then the PAE files are strongly advised, because they increase security, even with less than 4 GB RAM A reinstallation will create a /boot of 124 MiB, which gives ample headroom.
I have the same situation and I see that release 146 will have a new kernel as part of the update.
After reading through the posts and documentation I feel somewhat confident in doing a reinstall.
To confirm the steps: backup the current system (I assumes this will save all the firewall settings and rules), backup the addons, shutdown and reboot the new 64 bit ISO, run through the installation procedure, apply system backup, install addons, and apply addon backups.
If your systems support x86_64 it is a good time to update. core146 will not ship the pae kernel anymore so if you have more than 4GB you have to migrate in every case.
i586 is legacy! The kernel is not really tested anymore, because the developers and most user / distros not use 32bit anymore.