There's a couple of problems here we need to address...
1) features are listed on /solr/index.html, but there is also a right nav link to /solr/features.html
2) duplicate content on both /solr/features.html and /solr/index.html that will only increase that confusion
3) "Title" metadata from features.mdtext appearing the boxy of /solr/index.html
4) #1 & #2 both affect the /core/... urls as well (that features.mdtext evidently doens't use the "Title" attribute tough)
The fixes i would suggest are...
a) add a redirect for /solr/features.html -> /solr/ (and likewise for core)
b) remove "Features" from the right nav
c) either remove the "Title" metadata from pages being included, or stop doing this as an include and put the content direclty in index.mdtext – i would suggest the later since it will make it more straight forward for editing in the future.