I posted an EXTREMELY lengthy post about multiple ways of resolving "unremovable" quest entries, but this was about 6 months ago before all the posts in this forum were digested.
One way is to download two mods called called "journalfix" and "questfix" which were designed to address quest and jounal bugs that were *not* addressed after the last patch.
These plugins can be found here:
http://www.strong-family.net/morrowind/These plugins are a preventative measure however. They will not correct bugs that already appear in your journal.
Also, you can try editing your save file as if it were a plugin, and finding a way to set the "finished" bit in your quest entry. You'll have to search for some utilities for this to be done. If you find out, please post your results here.
Also, you can physically remove your quest entry from the journal. While this prevents your quest from showing up in the "completed list", unfortunately in removes your quest from the "view all" list as well. All relevant entries for the quest in your regular journal however will remain there (as well as all the hyperlinks I believe).
Possible programs you can use are MSGE, TESPDC, TESAME, among others. Try to open your save file as if it were a plugin.
I just wish I could give you a link to that discussion...