I remember the proposal you refer to - it was suggested just over a year ago in one
person's blog. However, the proposal was not as you state to "delete all submitted
bugs" - the proposal was to close all open bug reports for previous versions of the
software. The idea was that users could reopen issues if they could still reproduce
them. It was suggested because at the time the KDE bug database was clogged with
a huge number of bug reports, including many duplicates and ones that had already
been fixed; so much so that seemed like an impossible task to go through them all.
Now personally, I don't agree with this idea either. However it's important to point
out that it was most definitely *not* put into effect, and it shouldn't therefore be put
forward as a reason not to use KDE. This was all before the massive bug triaging
effort that has gone on in the last year which has improved the situation markedly.
IMO, KDE has shown that it does care about bug reports and it now does have
processes in place to deal with them effectively.