So here's what I did to perform the merge requested in the meta-post you linked:
- Synonymize python-2.6 into python-2.x
- Rename python-2.7 into python-2.x (I botched that one)
- Synonymize python2.6 into python-2.x
- Synonymize python2.7 into python-2.x
- Synonymize python2.x into python-2.x
Source: The Tag synonyms page
I guess that the root cause of this issue might be in the order of the first two steps...
Some things that may explain the different behaviours:
- Renaming the tag did not merge it (??). There's 1k python-2.7 questions, but only ~50 python-2.x questions
- Caching / Denormalization in the database?
I apparently just didn't use the rename tool correctly and botched something in the process... I have just now merged [python-2.7] into [python-2.x]. The inconsistencies you've seen should be fixed modulo caching.