prerequisites for test:
Any text with two consecutive misspelled words.

Steps to reproduce:
1. Take a paragraph with 2 or more consecutive misspelled words underlined red by the spelling feature like this one.

2. type <F7> or "extras/spelling+grammar"

Assume two consecutive words are marked as wrong (underlined by red waves) by the spelling check.

3. The 1st wrong word will be displayed in the correction window in red letters. The user might change the spelling manually or select a proposed word from the list or ignore it (type or press button change or ignore). Then the 2nd wrong word is displayed in red letters. So far - so good. If you now add manually a new leading letter to the 2nd word, the 1st word will be displayed in red again. Typing "ignore" will reverse the previously made correction and the 2nd word shows up in red letters again EXCEPT the first leading letter you added before (it occupies the position where the space has been before).

Apparently the string limits are not properly set and might include the space in between the words.

Operating System: GNU/Linux Debian wheezy

Corollary:
Loss of hard formats in the whole paragraph when typing in a non-red area of spell-checker window.

Typing anything outside the red letters will trigger LO to jump to the beginning of the paragraph and start over with the correction process in that paragraph. All misspelled words previously ignored will show up in red again.
But the main problem is, that the whole paragraph lose all of its hard formats (bold, hidden etc.).