Comments from the wiki page:

marc b says:

And much more important the buildstep collapse is destroying the layout completely. I would like to be able to deactivate the collapse-feature at all (I do not need that). Maybe release a different plugin for that.

Geri Broser says:

Why does this plugin "wrap all buildsteps into collapsible sections"? It's called Line Numbers Plugin, not Line Numbers and Collapsing Buildsteps Plugin.

This is against SoC and there's another plugin for this: Collapsing Console Sections Plugin.

I'd sometimes like to have line numbers in my log but I hate those collapsed sections fervently. They make this plugin unusable for me.