The verb "hear": regular or irregular

[Torsten]

The only reason why somebody would classify as 'irregular' is that you don't add 'ed' but just 'd' because the infinitive already ends in 'e'. Other than that, there is isn't anything 'irregular' about the verb 'lie' so it behaves pretty well.

TOEIC listening, photographs: A laboratory

[Dozy]

I don't think that in itself can be a reason because thousands of verbs end in "e" and just add "d". I think a more likely justification might be the appearance of "y" in the -ing form. But, as I say, I would personally consider that to be one of the rules of formation of regular verbs.