Comment 8 for bug 361843

Same here.
Some things I noticed:

Kile is only slow in some files. If multiple files are open in different tabs, I can write fast in some and in some not.

Deleting more and more text in one slow file, I realized that the responsiveness seems to be different in different paragraphs. I can't say that for sure, but I have the impression, that very long lines seem to trigger that effect. If I open a new, empty file, kile is fast. If I add many short lines, \sections etc., it is still fast, until I add a very long line (see attached example). Interesting enough, kile is than only slow, if the long line is shown on my screen. If I scroll up, so that the long line is out of the window, kile behaves fast. Kile gets even slower, if the long line gets longer (see second attachment).

If I have less then about 500 lines in one document, kile seems to become faster (still not really fast, especially when highlighting text with Ctrl+Up oder Down).