I'm prepared to give you a lot of examples (which other people might value differently). From the unfortunate consequences of the 'branches are files (and therefore tags are easily mutable by default and surprisingly hard to pin down)' to usual "I just committed, why does 'svn log' not show that?", to git bisect, to git clean and the stubbornness with which svn refuses to even consider implementing that.
that sounds like process-issues... not SVN issues.
tags should not be committed to... end-of-story.
as for 'svn-log not showing commits'... I've never heard of that one in the last decade of using it... I'm genuinely interested in how that came about.