Rylox wrote:Players are not able accept a summon received within an instance after leaving it.
IE: Receive summon > hearth to repair/buy reagent > accept summon.
Amon wrote:This is not true, it was added late in TBC: "Patch 2.4.0 (25-Mar-2008): Ritual of Summoning can be used to summon players into instances if they meet the instance requirements."
You are talking about completely different things.
What the OP describes as a bug is the fact that if a player receives a summon in an instance, from another player,
who is also in that instance, then hearthstones out of the instance before the summoning timer has expired, he is unable to accept the summon.
What you are referencing is the patch in which Blizzard made it possible for players to summon other players,
who are not in their instance, directly into it.
P.S. Regarding OP's bug report, I do not know whether it's a bug or blizzlike. I just wanted to clarify that the evidence presented so far is not pertinent to the discussion.