Eclipse update mechanism (called p2) actually at is core is very powerful and can actually find out/remedy the installation/update but it was just never exposed in the UI used by Eclipse IDE's.
Simply explained before Kepler p2 would just try and do exactly what you told it to "install these 2 plugins" and if its dependencies somehow conflicted it would give up ("could not complete operation").
In Kepler if this situation occurs p2 will try remedy the situation and try find out which plugins would need to be updated or maybe even downgraded to make it possible for you to install your plugins.
Thus we are some that actually care and do what we can to improve it - this feature got in with help from @prapicault
And for full disclosure i'm @maxandersen from the conversation OP linked to and lead of JBoss Developer Studio.