I know the underscore between webXX and uYY was removed due to security concerns in v2.2.20 (SVN r918) However, phpmyadmin has the nice LeftFrameDBSeparator option that allows to display a tree-like structure (here: all databases belonging to one web) However with no separator at all this is difficult. Should we reintroduce another separator? What about a dash? Note: phpmyadmin versions > 3.2.0 allow multiple separators to be specified.
The problem with changing the separator is that all existing databases in this ispconfig install can not be edited in ispconfig anymore afterwards, so I'am not sure if its worth to introduce a new separator when it breaks all old setups. As you might remember, we had the same problems as we ahd to remove the old separator.