Is there any chance someone could make a script that changes @username #hashtag strings sent in convos for a clickable string linking to the profile of that person in twitter and in a search request with that hashtag?

Example:

do you know @warmth? --> my profile
are you planning to go to #twiteq? --> search this hashtag in search.twitter.com


This idea can be very usefull and could become in a huge script later with many options, visualizations of pics, etc...

Unfortunately, it is not possible to do exactly what you suggested.

• We can't make links with a text that differs from the link URL. Messenger is responsible for making links clickable and it would be a serious concern when people could send links with a different text. Malicious users could send links which look like they're safe but will actually send you to a very nasty place.
  
• If we were to replace the incoming message by the plain URL, this replacing URL can't be longer than the original text (@warmth or #twiteq) because Messenger has already allocated the buffer to fit the message in - see notes in OnEvent_ChatWndReceiveMessage. Chances are very rare that you could make a URL which is shorter than the original text, even with some kind of URL shortening applied.