First a little observation if I may .. including some self-criticism.
I do think that in some of these long debates we are all tending to reply without taking the RAW but rather a paraphrase thereof which is at times very different. I give myself a slap because in being rather tired, thanks to little Sashca, I find myself in danger of doing the same thing at times -and even doing it once or twice
To clear this one up as MikeK righlty points out above (but to avoid any additional confusion)
THE SECTION ON CHARGING
States that you cannot charge the flank of a base that is already in
Melee. This is to allow 2 BGs to charge at impact, one of which can hit a side edge. There is nothing to stop such ganging up of a single BG at impact where opportunity arises. Indeed it is surely good tactics.

However this is only at IMPACT when the target BG is unengaged at the start of the IMPACT phase. Hope that makes sense.
THE SECTION ON FEEDING IN MORE BASES...
Alas is loosely titled and should have really said into an existing combat perhaps, we rather loosely thought of a melee as being something that you were in once you had fought an IMPACT phase, but didn't put a glossary entry to this effect (personal reflection only). We used melee to mean not in IMPACT phases perhaps.
However the first line is very specific and quite accurate.."a battle group involved in
close combat can". Close combat is defined in the glossary as having had a combat round - impact or melee.
Hope that clarifies this and avoids any confusion that by dealing with (a) it might be confusing (b) etc.
Si