Not working.

I did a few tests and what I found is if it finds a match, it replaces the word with itself instead of the replacement. (as noted by an upper and lower case change)

For example:

I put in a filter for "speaking" and it changed Speaking into speaking.

Editing the filter to "Speaking" changes speaking to Speaking.

Using "SPEAKING" changes all variants of the word "speaking" to all caps. Vice versa with all lower case.

Even using just the first two letters, it does the same thing. Similar if those two letters are in the middle of words. It just replaces them with themselves, only capitalizing or lowercasing, depending on what you put in the filter.

The Replace With word has no impact.

Edit: I put in a support ticket with my findings.