There is serveral quests that can longer be started by talking to the quest NPC or by quest sharing once certain follow-up/other quests are completed, but are still listed as incomplete for that character.
Examples from personal experience on my main Tvlfrosty - Mograine:
- Ragnar Thunderbrew (started at Enohar Thunderbrew in Netherwind Keep)
- The Corruption Abroad (started at Argos Nightwhisper in Stormwind City)
- The Temple of the Moon (started at Sister Aquinne in Darnassus)
- The QuarterMaster (started at Mountaineer Boombellow in Alterac valley)
- Find Bingles (started at Gnoarn in Ironforge)
- The Lost Dwarves (started at Prospector Stormpike in Ironforge)
Steps to reproduce the issue
- For example the quest: Ragnar Thunderbrew
- Either start the quest then abandon it or don’t start it at all.
- Get someone to share the Hurley Blackbreath quest with you.
- Complete the Hurley Blackbreath quest.
- Now since the Ragnar Thunderbrew quest was not a hard requirement, the quest npc that should have given you that quest thinks you already completed the (pre-)quest, but this is not the case.
I would really appreciate it if there was a way these quests could still be completed.
PS: To clarify "skipping" these quests was never my intention as it may seem so in the reproduction steps, I simply did not know they were there while levelling my character.