can you use the codes for such i.e instead of [&] type [&]

On further investigation, it seems to have only affected pre-existing symbols from before the normalization. If I type new tags using the same symbols, they work correctly, so no need for encoding them. However, I would like to know how to:

1 Go back and bulk-adjust all pre-existing tags so I don't have to manually edit every post.

EDIT: #1 The old / altered tags can be globally renamed in the Tags editor.

2 Delete old / unused tags from the "autocomplete pool" of tags, so that when I type a string in the tags field, the old tags don't show up as options, but only the new ones.

EDIT: #2 is answered here: http://b2evolution.net/man/tags-tab. To enable tag modification for a specific group, go to:
Users -> Groups -> GroupName -> System Admin Permissions -> Settings, and select Edit\Delete all. That setting controls whether a group can modify tags. I'm sure it controls other things also. Would be nice to know what specifically.

jj.

In previous versions some open source contributor had contributed really bad code for storing special chars in tags. We have changed that to a clean UTF-8 storage but there is no way to auto-convert the old chars to the new ones because no info is stored on the charset of the old chars.

In any case, you can edit the altered tags to give them back their special chars. No need to touch the actual posts.

Yeah I had this problem too. I simply dumped the new-broken-replaced table, and reimported the old evo_item_tags table :D

@tilqicom bad idea. You will have other problems down the line and you will report them as bugs, which they are not.

You should normalize your DB and fix the special chars manually in the tags editor.