I can see in the task list for my PC system that a couple of computations have got the client state "Compute error" occasionally. I can look into each of them by the results web display. But I find this user interface to find out corresponding error reasons not so convenient as I imagine it could be.

The BOINC software has got an infrastructure to generate some statistics. Now I am looking for tools which can visualise the error distribution in an improved way to increase the chances for fixing involved open issues.

Is any automatic analysis performed on the returned exit codes within work units?
Is an automatic categorisation performed for computation failures so that an efficient drill-down into interesting issues would be supported?

What post-run analysis done on resturned results is a project matter and has nothing to do with BOINC. The best thing for you to do is ask each of the projjects what they do.