It's six characters, and yes, it's useful. You have stuff to read for the rest of the day:
And a thousand others. Per Shog's answer to Why are trivial edits discouraged?:
The Stack Exchange model for editing is a hybrid of these two approaches. While it falls somewhat closer to the wiki model than the forum model, it deviates from the latter in a few key areas:
Edits made by the same editor in a short period of time are collapsed: no matter how many times a post is edited within a 5-minute window, only one revision is stored (as long as only one editor is involved). This largely eliminates the need for a "minor edit" feature.
Tools for comparing revisions are much more limited: only revisions directly adjacent in the chronology can be compared.
Outside of Community Wiki posts, an original author is always maintained and clearly identified even if substantial changes have been made by other editors since the post was created.
Together, this hybrid system allows for a much simpler, much easier-to-read, easier-to-navigate user interface. However, this comes at a cost: trivial one-off edits must be discouraged in favor of more comprehensive edits.
If merely maintaining a simple UI were the only concern, it might be worthwhile to consider an optional "expert" mode that allowed minor edits at the cost of a more involved UI. However, there's a much bigger concern...
This is deep into the design of the system. Your edit must be non-trivial. This has already been discussed enough, and you can find out more by searching in meta.SE or meta.SO.
You can instead
- Leave a comment pointing out the error
- Leaving the post for the higher-rep users to edit
- Ping someone in chat and ask them to edit
- Make your edit more substantial. I rarely edit less than 6 characters while being a privileged user myself.
I hope this clears things up.