How to correct some spelling mistakes while there's a limitation that said
Edits must be at least 6 characters; is there something else to improve in this post?
You can always find something else to correct - in this snippet I'd maybe change "the key of the receiving party" or 'the used password" to the password they have used, and include that you've done the additional grammar fixes cause of the lameness filter. Eventually, once you've enough reputation, you can make even small edits directly.
I use the html codes < strike> and < /strike> (without the spaces).
Since this is frown upon, I suppose you can add blank spaces and new lines (since they will be removed automatically).