Currently it allows you to change the last 4 out of 5 tags for as long as you can edit the post. It doesn't let you change the first tag ever, because of the way it is used to save the data in the blockchain. It would probably be a pretty major change to change that actually - probably requiring a hardfork.
I do think an auto complete (if done right) could add a lot of value. For example, if you are writing a post about your pet, do you use the 'pet' or 'pets' tag? If it could show both, along with some type of usage statistics, so users could make an educated decision on which one(s) to use, that would be pretty cool.
I hate autocorrect systems. Autosuggestion systems. When my computer thinks it is smarter than I am, I hate it. :)
I type in "pet" and it wants to suggest "pets" so I delete the "s" and it wants to put it back again. I get angry. "
Yes, I know pets is more popular, but I wanted to create my own pet tag. now leave me alone!"
...but no, the autocorrect, autosuggest gets in the way... "surely you wanted this instead didn't you?" - NO!
...but you wanted me to recommend it didn't you?
NO! If I want you to suggest or recommend something, I'll ask you.
.....yeah, autocorrect and autosuggestions really bug me. It is a petpeeve of mine.
P.S. I didn't know you could change your tags on the post except the primary tag. I'm now smarter cuz of you. Thanks for that info!
Haha, well if it is implemented, I will make sure to suggest a setting where you have the option to turn it off :)