Glassdoor reviews are mostly anonymous and sometimes I have seen angry people venting out there. I feel some of the positive reviews in Glassdoor are in because someone in the company pushed people to write them.

Thats right. The Org generally gets some of its marketing team members to write reviews and get it posted on Glassdoor.

Why do someone send a link that requires a subscription to read?

Because sometimes quality journalism is worth finding. If I say I read a lovely article in a magazine, are you going to fix at me for discussing something that cost money to access?

If I can get a summary before I pay for access it will be good, than proceed with buying.

Here the guideline to help us from the FAQs: It's ok to post stories from sites with paywalls that have workarounds.