I’ve used a Kindle since 2012 and I don’t think I have ever seen that kind of dictionary issue. On my Kindle, even though text highlighting behaves as you describe, dictionary lookups still work because punctuation is stripped before searching. For example I just highlighted “doing,” (including the comma) and the dictionary shows the definition of the word “doing”. I wonder if it works differently for languages other than English. (There is a different problem, that the stemming/trimming can be too aggressive and gets you irrelevant words in searches — i.e. ‘several’ when you search ‘severance’.)